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The Impact of Gross Fixed Capital Formation Growth on the Economic Growth of the Philippines: A Time Series Approach
An Empirical Paper
Presented to
The Faculty of the School of Economics
De La Salle University
In Partial Fulfillment of the Requirements in ECOMET2
Submitted by:
Ibas, Shaira Marie S.
11239190
Submitted to:
Dr. Cesar Rufino
Table of Contents ...................................................................................................................................................................... 1
INTRODUCTION ............................................................................................................................................ 5
Background of the Study ............................................................................................................................... 5
Statement of the Problem ......................................................................................................................... 6
Objectives of the Study ............................................................................................................................. 6
Significance of the Study ........................................................................................................................... 7
Scope and Limitations ............................................................................................................................... 7
REVIEW OF RELATED LITERATURE .............................................................................................................. 8
THEORETICAL FRAMEWORK ...................................................................................................................... 11
Neoclassical Growth Theory ................................................................................................................... 11
Solow Growth Model ................................................................................................................................ 11
OPERATIONAL FRAMEWORK ..................................................................................................................... 13
Data ............................................................................................................................................................. 13
Description of the Variables Used .............................................................................................................. 13
A-Priori Expectations ............................................................................................................................... 14
INITIAL TESTS .............................................................................................................................................. 16
Unit Root Tests ........................................................................................................................................... 16
Graph Analysis ............................................................................................................................................ 16
Dickey-Fuller Unit Root Test ........................................................................................................................ 17
Phillips-Perron Unit Root Test for GDP Growth ........................................................................................... 18
Test for Lag Structure ................................................................................................................................. 19
Hendry’s Top-Down Approach .................................................................................................................... 19
Alt and Tinbergen (Ad Hoc Estimation) Method ......................................................................................... 20
Test for Cointegration ................................................................................................................................ 20
Augmented Engle-Granger Test .................................................................................................................. 21
Johansen Cointegration Test ....................................................................................................................... 21
Test for Causality ........................................................................................................................................ 22
Augmented Engle-Granger Causality Test .................................................................................................. 22
STATIC MODEL ............................................................................................................................................ 25
Initial Static Model ..................................................................................................................................... 25
Variance Inflation Factor Test for Multicollinearity .................................................................................... 25
Breusch-Pagan Test for Heteroscedasticity ................................................................................................ 26
Breusch-Godfrey Test for Autocorrelation .................................................................................................. 26
Final Static Model ....................................................................................................................................... 27
Prais-Winsten Robust Regression for Corrective Measures ........................................................................ 27
Final Static Model ....................................................................................................................................... 28
DYNAMIC MODELS ..................................................................................................................................... 29
General Distributed Lag Model .................................................................................................................. 29
Initial General Distributed Lag Model ......................................................................................................... 29
Initial Regression ......................................................................................................................................... 29
Test for Multicollinearity ............................................................................................................................ 29
Test for Heteroscedasticity ......................................................................................................................... 29
Test for Autocorrelation ............................................................................................................................. 30
Prais-Winsten Robust Regression for Corrective Measures ........................................................................ 30
Final General Distributed Lag Model .......................................................................................................... 31
Koyck Infinite Distributed Lag Model ........................................................................................................ 31
OLS Estimation ............................................................................................................................................ 32
Test for Multicollinearity ............................................................................................................................ 32
Test for Heteroscedasticity ......................................................................................................................... 33
Test for Autocorrelation ............................................................................................................................. 33
Final Koyck Infinite Distributed Lag Model Using OLS ................................................................................ 33
Two-Stage Least Squares (2SLS) Estimation ............................................................................................... 35
Test for Autocorrelation ............................................................................................................................. 36
Final Koyck Infinite Distributed Lag Model Using 2SLS ............................................................................... 36
Almon Polynomial Distributed Lag (PDL) Model ....................................................................................... 38
Initial Regression ......................................................................................................................................... 38
Test for Multicollinearity ............................................................................................................................ 39
Test for Heteroscedasticity ......................................................................................................................... 39
Test for Autocorrelation ............................................................................................................................. 39
Prais-Winsten Robust Regression for Corrective Measures ....................................................................... 39
Final Almon Polynomial Distributed Lag Model .......................................................................................... 40
Autoregressive Distributed Lag Model (ARDL) .......................................................................................... 41
Initial Regression ......................................................................................................................................... 41
Test for Multicollinearity ............................................................................................................................ 41
Test for Heteroscedasticity ......................................................................................................................... 41
Test for Autocorrelation ............................................................................................................................. 42
Final Autoregressive Distributed Lag Model ............................................................................................... 42
CONCLUSIONS AND RECOMMENDATIONS ............................................................................................... 43
BIBLIOGRAPHY ............................................................................................................................................ 44
INTRODUCTION
Background of the Study
In terms of finding ways on how to improve an economy’s performance, investment
has always been one of the most common instrument. Investment is usually measured
through gross fixed capital formation, also called net investment, which is defined as the
“net amount of the fixed capital acquired.” It indicates the rise in the capital stock minus
the removal of fixed assets (Pettinger, n.d.). At the one hand, economic performance is
not only determined by investments because of there are other factors such as
consumption, government expenditures, exports and imports (Blanchard & Johnson,
2013). Given that, it is possible that it is not investment on buildings, machineries,
infrastructures and equipment that leads to an increase in the growth of the economy,
and that it may be the growth of the economy which spurs the increase in the capital
formation of an economy. This issue has actually been in numerous literatures for quite
some time already. In fact, in one of Kuznet’s studies, it was said that there are situations
wherein economic growth happens before the capital increases (Blostrom, Lipsey &
Zejan, 1993).
The possibility that investments may not affect economic growth and the possibility
that investment determines economic growth will be discussed in the Review of Related
Literature of this paper wherein studies conducted in different countries and regions will
show varying results.
Statement of the Problem
This study aims to answer a number of questions regarding the relationship of
gross fixed capital formation growth and GDP growth. These questions are the following:
1. Is the gross fixed capital formation growth significant in determining the GDP
growth of the Philippines?
2. Is gross fixed capital formation growth a driver GDP growth or is it GDP growth
that is a driver of the gross fixed capital formation growth?
3. How long does gross fixed capital formation growth formation take in order for it to
affect GDP growth?
4. How can the Philippines improve its economy in terms of investments or capital
formations?
Objectives of the Study
This study aims to:
1. Determine the relationship of gross fixed capital formation growth and GDP
growth using dynamic econometric models.
2. Find out the causality between gross fixed capital formation growth and GDP
growth and determine whether the gross fixed capital formation are crucial to
GDP growth in the long-run.
3. Determine how long gross fixed capital formation growth will affect GDP growth.
Significance of the Study
This paper aims to show the relationship of gross fixed capital formation growth
and GDP growth because there may be a need to reconsider the policies of the
government like improving the physical and social infrastructures such as road and
railway constructions or renovations and school and hospital constructions. Given that
Philippines aims to develop and increasing investments and capital formations are taken
into consideration as instruments, this paper will be able to show its possible effects on
the economic growth. Given this, the paper may serve as a basis in future policy-making
with regards to determining how much should be released for capital formation to make
the economy grow further.
Scope and Limitations
This study concentrates on gross fixed capital formation as a determinant of
economic growth, thus, not taking into account other factors such as consumption,
government expenditure, exports and imports. In this study, the data used were taken
from World Bank’s World Development Indicator covering years 1961 to 2013 which
means that the dataset consists of 53 observations for both gross fixed capital formation
growth and GDP growth.
REVIEW OF RELATED LITERATURE
Capital formation is an established determinant of the economic growth. Given this,
numerous studies were done that used it as an explanatory variable for GDP. The
remaining parts of this section will discuss studies that will show the relation of gross fixed
capital formation and GDP.
Some studies say that it is investments that affect GDP growth. One of which is
the study in India where it was observed that the current investment rate has increased
dramatically since the 1950s. Because of the said increase in investment rate, the
researchers evaluated its effects on the growth of the economy. The results of the said
study showed that although the investment rate is high, its contribution to the GDP per
worker in India is not that high. Furthermore, the study showed that the high investment
rate today will not have a huge effect on the economic growth of India in the future and
that higher investment rates in the future may also have small effect on the growth of the
economy (Robertson, 2010). Another study that poses the same result is the study of De
Long and Summers (1991). Using the machinery and equipment investment and GDP
growth data from 1960 to 1985, the result indicated that a percent increase in GDP that
is spent for machineries and equipment will increase GDP growth by one-third of the
recorded annual percentage point.
There are also studies that say that it is GDP growth that affects investments. In
the study of Blomstrom, Zejan and Lipsey (1993). From the said study, investment was
measured in terms of fixed capital formation contribution to GDP. Simple and multiple
regressions were done using different factors that affect GDP growth. Aside from this,
causality test was also done and it showed that the effect of increase in fixed capital
formation towards the increase in GDP growth is lesser than the effect of increase in GDP
growth towards the increase in fixed capital formation. The researchers also found out
that high fixed capital investment rates contributes to boosting the GDP per capita growth,
however, it is not the only determinant of GDP growth. A similar study is done using the
gross domestic investment and GDP data for Middle East and North Africa (MENA) for
years 1970 to 2010. The said study of Mehrara and Muhsai (2013), indicated that there
is unidirectional causality between GDP and gross domestic investment such that it is
GDP that affects gross domestic investment. Thus, having higher GDP will allow higher
gross domestic investments.
Aside from determining which variable affects which, researchers have also been
interested in determining whether GDP growth and capital formation have long-run and
short-run relationship. A study was conducted in Nigeria which showed that gross fixed
capital formation has no short-run relationship to GDP growth. In addition, the same study
used vector autoregression to determine the long-run relationship of the two variables.
The results showed that gross fixed capital formation, exports and the lagged GDP growth
have long-run relationship with the current GDP growth. The same study also showed
that GDP has a unidirectional causal relationship with exports, gross fixed capital
formation, import and savings (Kanu & Ozurumba, 2014). Another study that showed the
short-run and long-run relationship of capital formation and economic growth is the study
of Mehta (2011). The study used data from India and employed cointegration and vector
error correction model to determine the short-run and long-run relationship of capital
formation and GDP. The cointegration test results showed that capital formation and GDP
have long-run relationship. However, the vector error correction technique yielded
insignificant coefficients which implies that the lagged values of the logarithm of GDP do
not affect capital formation.
Given the related literature discussed, this study aims to fill the gap in the lack of
empirical analysis on the relationship of GDP growth and gross fixed capital formation
growth in the Philippines.
THEORETICAL FRAMEWORK
When talking about investments, what are taken into consideration are business
fixed investments, residential investments and inventory investments. These investments
pertain to equipment, machines, houses, raw materials, work in progress and finished
goods that are stored (Mankiw, 2012). Given this definition, and the fact that gross fixed
capital formations are comprised of land improvements, machinery, equipment and
construction spending, then it is an investment.
Neoclassical Growth Theory
The neoclassical growth theory was first developed by Robert Solow and J.E.
Meade in the late 1950s and early 1960s. The said theory gives emphasis on the
relationship of capital accumulation and savings to economic growth. Specifically, the
theory states that there are two main factors of production such as labor and capital. Later
on, technology was also added in the production function. The claim that output affects
capital accumulation is presented through the Solow growth model.
Solow Growth Model
This model was created by Robert Solow in 1956 which showed the
factors that affect economic growth. From the Solow growth model, it can be
concluded that in the long run, the level of capital determines the level of output
produced. In addition, the level of output determines the level of savings and
investments, and level of capital accumulation. By holding the population,
participation rate and unemployment rates constant and that there is no
technological improvements, it can be said the increases in capital per worker
will increase output per worker. On the other hand, because private savings
equate to investment and is in proportion with income, then investment is in
proportion with income as well. Thus, when the output increases, savings also
increase which in turn increases the investments. Moreover, if it happens that
the capital per worker and output per worker are low, and investment is greater
than the value of depreciation, it will result to increase in capital per worker
and output per worker as time goes by. However, if capital per worker and
output per worker are high, and investments is less than the value of
depreciation, then capital per worker will decrease as time goes by (Blanchard
& Johnson, 2013). These relationships can be shown through the table below
such that the green arrow shows the first relationship, while the blue and
purple arrows indicate the second relationship.
Figure 3.1: Capital, Output and Saving/Investment (Blanchard & Johnson, 2013).
OPERATIONAL FRAMEWORK
Data . tsset year
time variable: year, 1961 to 2013
delta: 1 unit
In using dynamic models in econometrics, it is essential to ensure that the data
used is time series data. In this study, the data for the Philippine gross fixed capital
formation and economic growth are taken from the World Bank and it covers years 1961
to 2013, giving us 53 observations. Before proceeding with the tests and regressions, the
command tsset is used in Stata 12 in order to set the variables into time series form.
To show the relationship between gross fixed capital formation and GDP growth,
the data should be tested in terms of its stationarity, cointegration and causality which will
be shown in the next chapter of this paper. The table below shows the summary of all the
variables in the study.
. summarize
Variable | Obs Mean Std. Dev. Min Max
-------------+--------------------------------------------------------
year | 53 1987 15.44345 1961 2013
gfcfgr | 53 5.435404 11.0547 -31.49475 31.98448
gdpgr | 53 4.167703 3.027177 -7.323683 8.920647
Description of the Variables Used
It is essential to identify the dependent variable and independent variable and its
specifications first before dealing with the tests and the regressions. The table below
shows the descriptions of the variables used.
DEPENDENT VARIABLE
gdpgr Gross domestic product
growth
It is the annual percentage
change of GDP which is
based on the constant
local currency.
INDEPENDENT VARIABLE
Variable Label Description
gfcfgr Gross fixed capital
formation growth
It is the annual percentage
change of gross fixed
capital formation which
consists of land
improvements,
machineries, equipment,
construction spending, etc.
at market prices based on
the constant local currency.
A-Priori Expectations
INDEPENDENT VARIABLE
ALGEBRAIC SIGN EXPLANATION
gfcfgr + More fixed capital formation
will mean that more roads
and facilities will be
constructed. Given this,
transferring of goods will be
faster and thus, increasing
the income of the country.
The model will be written as:
𝑔𝑑𝑝𝑔𝑟 = 𝛽1 + 𝛽2𝑔𝑓𝑐𝑓𝑔𝑟 + 𝑢𝑡
INITIAL TESTS
Unit Root Tests This is also known as the test for stationarity which is a requirement in a time
series analysis. The reason behind this is that non-stationary data will lead to results
that can be used for making conclusions. Therefore, it means that if a data is non-
stationary, the results that will be taken from different periods will be different because
the mean and variance over time also differ (Gujarati & Porter, 2009).
In order to check the stationarity of gross fixed capital formation and GDP
growth, the graph of both variables will be analyzed. In addition, unit root testing such
as Dickey-Fuller test and Phillips-Perron test will also be used.
Graph Analysis
. tsline gdpgr gfcfgr
-40
-20
02
04
0
1960 1970 1980 1990 2000 2010year
gdpgr gfcfgr
It can be observed that the line graphs for both GDP growth (gdpgr) and gross
fixed capital formation (gfcfgr) do not show any trend or breaks that may lead to making
the data for variables to become non-stationary. Given that the graph shows that the data
for the variables are stationary, it is still best to use other tests to ensure that this
conclusion is correct.
Dickey-Fuller Unit Root Test . dfuller gdpgr
Dickey-Fuller test for unit root Number of obs = 52
---------- Interpolated Dickey-Fuller ---------
Test 1% Critical 5% Critical 10% Critical
Statistic Value Value Value
------------------------------------------------------------------------------
Z(t) -4.106 -3.577 -2.928 -2.599
------------------------------------------------------------------------------
MacKinnon approximate p-value for Z(t) = 0.0009
. dfuller gfcfgr
Dickey-Fuller test for unit root Number of obs = 52
---------- Interpolated Dickey-Fuller ---------
Test 1% Critical 5% Critical 10% Critical
Statistic Value Value Value
------------------------------------------------------------------------------
Z(t) -5.360 -3.577 -2.928 -2.599
------------------------------------------------------------------------------
MacKinnon approximate p-value for Z(t) = 0.0000
Given the Dickey-Fuller unit root test above, the result shows that both GDP growth
and gross fixed capital formation growth are stationary which means that they do not have
unit roots. Therefore, there is no need to get the first difference of both variables. This is
so because for GDP growth, the absolute value of the test statistic (-4.106) is greater than
the absolute value of the critical value at 5% (-2.928). On the other hand, for gross fixed
capital formation growth, the absolute value of its test statistic (-5.360) is also greater than
the absolute value of the critical value at 5% (-2.928). Furthermore, if the p-value will
serve as the basis to know the stationarity of the data, the result will also be consistent
as the p-value for Z(t) for both GDP growth and gross fixed capital formation growth are
less than 0.05 which means that the null hypothesis that there is unit root is rejected.
Phillips-Perron Unit Root Test for GDP Growth . pperron gdpgr
Phillips-Perron test for unit root Number of obs = 52
Newey-West lags = 3
---------- Interpolated Dickey-Fuller ---------
Test 1% Critical 5% Critical 10% Critical
Statistic Value Value Value
------------------------------------------------------------------------------
Z(rho) -26.591 -18.936 -13.316 -10.712
Z(t) -4.105 -3.577 -2.928 -2.599
------------------------------------------------------------------------------
MacKinnon approximate p-value for Z(t) = 0.0010
. pperron gfcfgr
Phillips-Perron test for unit root Number of obs = 52
Newey-West lags = 3
---------- Interpolated Dickey-Fuller ---------
Test 1% Critical 5% Critical 10% Critical
Statistic Value Value Value
------------------------------------------------------------------------------
Z(rho) -35.877 -18.936 -13.316 -10.712
Z(t) -5.300 -3.577 -2.928 -2.599
------------------------------------------------------------------------------
MacKinnon approximate p-value for Z(t) = 0.0000
The null hypothesis for the Phillips-Perron test is that there is non-stationarity or
that there is a unit root. In the case of GDP growth, the p-value of Z(t) is also less than
0.05 and the absolute value of the test statistic of Z(rho) (-26.591) is greater than the
absolute value of the critical value at 5% (-13.316). On the other hand, for the gross fixed
capital formation growth, the p-value of Z(t) is also less than 0.05 and the absolute value
of the test statistic of Z(rho) (-35.877) is greater than the absolute value of the critical
value at 5% (-13.316). Therefore, the result of the Phillips-Perron test implies that the null
hypothesis should be rejected, meaning there is no unit roots and the data is stationary.
Test for Lag Structure
It is important to determine the optimal lag structure to find out the longest period
of time that the lagged value of a variable can affect the current value of a variable (Hill,
Griffiths & Lim, 2011). To find out the maximum lag, Hendry’s top-down approach and
Alt and Tinbergen or the Ad Hoc Estimation Method will be used.
Hendry’s Top-Down Approach
. varsoc gdpgr gfcfgr
Selection-order criteria
Sample: 1965 - 2013 Number of obs = 49
+---------------------------------------------------------------------------+
|lag | LL LR df p FPE AIC HQIC SBIC |
|----+----------------------------------------------------------------------|
| 0 | -290.294 520.423 11.9304 11.9597 12.0076* |
| 1 | -282.624 15.34* 4 0.004 448.157* 11.7806* 11.8685* 12.0122 |
| 2 | -281.073 3.1029 4 0.541 495.815 11.8805 12.027 12.2666 |
| 3 | -278.582 4.9823 4 0.289 528.635 11.9421 12.1472 12.4826 |
| 4 | -277.269 2.6253 4 0.622 592.58 12.0518 12.3155 12.7468 |
+---------------------------------------------------------------------------+
Endogenous: gdpgr gfcfgr
Exogenous: _cons
The Final Prediction Error (FPE), Akaike Information Criterion (AIC),
Bayesian/Schwartz Criterion Information (SBIC) and Hannan-Quinn Information Criterion
(HQIC) will serve as basis to determine the optimal lag. The results from the table above
implies that FPE, AIC and HQIC shows that the optimal lag is one while SBIC shows that
the optimal lag is zero. Therefore, the optimal lag should be one since most of the
information criterion chose lag one.
Alt and Tinbergen (Ad Hoc Estimation) Method
. regress gdpgr gfcfgr l1.gfcfgr
Source | SS df MS Number of obs = 52
-------------+------------------------------ F( 2, 49) = 31.35
Model | 266.272143 2 133.136071 Prob > F = 0.0000
Residual | 208.105933 49 4.24705985 R-squared = 0.5613
-------------+------------------------------ Adj R-squared = 0.5434
Total | 474.378076 51 9.30153089 Root MSE = 2.0608
------------------------------------------------------------------------------
gdpgr | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
gfcfgr |
--. | .1987499 .0270498 7.35 0.000 .1443913 .2531084
L1. | .0222847 .0269705 0.83 0.413 -.0319145 .0764838
|
_cons | 2.975012 .3336207 8.92 0.000 2.304576 3.645448
------------------------------------------------------------------------------
Upon adding one lag of gross fixed capital formation growth to the regression, the
result showed that the lagged variable has a p-value of 0.413 which means that it is
insignificant. Therefore, the regression should stop at the first lag.
The results of both Hendry top-down approach and Alt and Tinbergen method are
consistent. Therefore, the optimal lag should be one.
Test for Cointegration
In this test, the movement of the variable together over time is considered to find
out whether there is a relationship between the two variables in the long run. This test
serves as a proof that the results are not spurious (Gujarati &Porter, 2009).
In this section, Augmented Engle-Granger Test and Johansen Cointegration Test
will be used to determine whether there is a long run relationship between gross fixed
capital formation growth and GDP growth.
Augmented Engle-Granger Test
. regress gdpgr gfcfgr
Source | SS df MS Number of obs = 53
-------------+------------------------------ F( 1, 51) = 64.10
Model | 265.379461 1 265.379461 Prob > F = 0.0000
Residual | 211.138226 51 4.13996522 R-squared = 0.5569
-------------+------------------------------ Adj R-squared = 0.5482
Total | 476.517688 52 9.16380169 Root MSE = 2.0347
------------------------------------------------------------------------------
gdpgr | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
gfcfgr | .2043549 .0255241 8.01 0.000 .1531132 .2555965
_cons | 3.056952 .3120249 9.80 0.000 2.430536 3.683368
------------------------------------------------------------------------------
. predict uhat, residual
. regress d.uhat l.uhat l.d.uhat
Source | SS df MS Number of obs = 51
-------------+------------------------------ F( 2, 48) = 12.59
Model | 93.7753949 2 46.8876975 Prob > F = 0.0000
Residual | 178.765914 48 3.72428988 R-squared = 0.3441
-------------+------------------------------ Adj R-squared = 0.3167
Total | 272.541309 50 5.45082619 Root MSE = 1.9298
------------------------------------------------------------------------------
D.uhat | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
uhat |
L1. | -.7331103 .1651285 -4.44 0.000 -1.065123 -.4010971
LD. | .100608 .1420287 0.71 0.482 -.1849597 .3861758
|
_cons | -.0410718 .2703671 -0.15 0.880 -.5846813 .5025377
------------------------------------------------------------------------------
The result shows that the t-ratio of the lagged residual is -4.44 that is less than the
critical value at 5% for a cointegration regression which is -3.37. Given this, the null
hypothesis that the residuals in the least squares is non-stationary is rejected. Therefore,
the residuals are stationary, and GDP growth and gross fixed capital formation growth
are cointegrated.
Johansen Cointegration Test
. vecrank gdpgr gfcfgr, lags(1)
Johansen tests for cointegration
Trend: constant Number of obs = 52
Sample: 1962 - 2013 Lags = 1
-------------------------------------------------------------------------------
5%
maximum trace critical
rank parms LL eigenvalue statistic value
0 2 -323.88075 . 46.2615 15.41
1 5 -308.25257 0.45178 15.0052 3.76
2 6 -300.74999 0.25066
-------------------------------------------------------------------------------
The trace statistic of rank 0 or line 1 (46.2615) is greater than the critical value at
5% (15.41). In addition, the trace statistic of rank 1 or line 2 (15.0052) is also greater than
the critical value at 5% (3.76). Given these, there is a strong evidence against the null
hypothesis that there are equations that are not cointegrated, meaning that the variables
are cointegrated with each other. Therefore, GDP growth and gross fixed capital
formation growth are cointegrated.
Test for Causality
Given that the variables have long-run relationship and are stationary, the cause
and effect relationship of the variables may be determined through testing for causality.
Therefore, at this part of the paper the question of “Is it gross fixed capital formation
growth that drives GDP growth?” and “Is it GDP growth that drives gross fixed capital
formation growth?” will be answered.
To answer this question, vector autoregressive model is ran prior to running the
command to determine the Granger causality of the variables.
Augmented Engle-Granger Causality Test
. var gdpgr gfcfgr, lags(1)
Vector autoregression
Sample: 1962 - 2013 No. of obs = 52
Log likelihood = -300.75 AIC = 11.79808
FPE = 456.0393 HQIC = 11.88439
Det(Sigma_ml) = 361.9671 SBIC = 12.02322
Equation Parms RMSE R-sq chi2 P>chi2
----------------------------------------------------------------
gdpgr 3 2.69515 0.2497 17.30546 0.0002
gfcfgr 3 10.4742 0.1433 8.698708 0.0129
----------------------------------------------------------------
------------------------------------------------------------------------------
| Coef. Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
gdpgr |
gdpgr |
L1. | .6255078 .1813128 3.45 0.001 .2701412 .9808745
|
gfcfgr |
L1. | -.05017 .0493318 -1.02 0.309 -.1468585 .0465186
|
_cons | 1.835601 .6817613 2.69 0.007 .4993736 3.171829
-------------+----------------------------------------------------------------
gfcfgr |
gdpgr |
L1. | 1.434962 .7046394 2.04 0.042 .0538945 2.81603
|
gfcfgr |
L1. | -.0176717 .1917191 -0.09 0.927 -.3934342 .3580908
|
_cons | -.5381844 2.649541 -0.20 0.839 -5.73119 4.654821
------------------------------------------------------------------------------
. vargranger
Granger causality Wald tests
+------------------------------------------------------------------+
| Equation Excluded | chi2 df Prob > chi2 |
|--------------------------------------+---------------------------|
| gdpgr gfcfgr | 1.0343 1 0.309 |
| gdpgr ALL | 1.0343 1 0.309 |
|--------------------------------------+---------------------------|
| gfcfgr gdpgr | 4.1471 1 0.042 |
| gfcfgr ALL | 4.1471 1 0.042 |
+------------------------------------------------------------------+
The null hypothesis for the first box is that the lagged gross fixed capital formation
growth does not Granger-cause GDP growth. The prob>chi2 shows that insignificance at
5% because it is greater than 0.05. This means that there is no evidence against the null
hypothesis. Therefore, the lagged gross fixed capital formation growth does not Granger-
cause GDP growth. On the other hand, for the second box, the null hypothesis is that the
lagged GDP growth does not Granger-cause gross fixed capital formation growth. For
this, the prob>chi2 is 0.042 which implies that it is significant at 5%. This means that there
is a strong evidence against the null hypothesis. Therefore, the null hypothesis is rejected
which means that the lagged GDP growth Granger-cause gross fixed capital formation
growth.
The results show that gross fixed capital formation does not Granger-cause GDP
growth. Because of this, the rest of the paper will be looking at the correlation of the
variables instead of claiming that gross fixed capital formation growth Granger-causes
GDP growth since it may result to incorrect results and interpretations. Thus, GDP growth
will be the dependent variable and gross fixed capital formation growth will be the
independent variable.
STATIC MODEL
Initial Static Model The estimates shown below are determined using Ordinary Least Squares estimation
method.
. regress gdpgr gfcfgr
Source | SS df MS Number of obs = 53
-------------+------------------------------ F( 1, 51) = 64.10
Model | 265.379461 1 265.379461 Prob > F = 0.0000
Residual | 211.138226 51 4.13996522 R-squared = 0.5569
-------------+------------------------------ Adj R-squared = 0.5482
Total | 476.517688 52 9.16380169 Root MSE = 2.0347
------------------------------------------------------------------------------
gdpgr | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
gfcfgr | .2043549 .0255241 8.01 0.000 .1531132 .2555965
_cons | 3.056952 .3120249 9.80 0.000 2.430536 3.683368
------------------------------------------------------------------------------
To validate the results shown above, the estimation results should be checked if it
violates the Classical Linear Regression Model (CLRM) assumptions. If in case it violates
the assumptions, there is a need to correct it which may cause the estimates to change.
The following sections of this chapter will present the tests and needed corrections.
Variance Inflation Factor Test for Multicollinearity
Multicollinearity occurs if there are two or more independent variables in the
multiple regression model that have perfect or exact linear relationship (Gujarati & Porter,
2009). To find out whether there is multicollinearity in the model, the variance inflation
factor test will be used. If the result of the mean vif is 10, it will imply that there is
multicollinearity.
. vif
Variable | VIF 1/VIF
-------------+----------------------
gfcfgr | 1.00 1.000000
-------------+----------------------
Mean VIF | 1.00
The result shows that mean vif is 1. Since this is clearly less than 10, then the
model does not suffer from multicollinearity.
Breusch-Pagan Test for Heteroscedasticity
One of the assumptions of Classical Linear Regression Model (CLRM) is
homoscedasticity which means that the variance of each disturbance term is constant
(Gujarati & Porter, 2009). To find out if the variance is constant or not, the Breusch-Pagan
heteroscedasticity test will be used.
. hettest
Breusch-Pagan / Cook-Weisberg test for heteroskedasticity
Ho: Constant variance
Variables: fitted values of gdpgr
chi2(1) = 2.24
Prob > chi2 = 0.1347
The p-value is 0.1347 which is clearly greater than 0.05. Given this, there is no
evidence against the null hypothesis that the variance is constant. The null hypothesis
will be accepted and thus, there is homoscedasticity.
Breusch-Godfrey Test for Autocorrelation
Another assumption under the Classical Linear Regression Model (CLRM) is that
there is no autocorrelation which means that the disturbance term of an observation is
not affected by the disturbance term of another observation (Gujarati & Porter, 2009). To
find out if autocorrelation exists, the Breusch-Godfrey test will be used.
. bgodfrey
Breusch-Godfrey LM test for autocorrelation
---------------------------------------------------------------------------
lags(p) | chi2 df Prob > chi2
-------------+-------------------------------------------------------------
1 | 6.135 1 0.0133
---------------------------------------------------------------------------
H0: no serial correlation
The test generated a p-value which is equal to 0.0133. This implies that the null
hypothesis that there is no serial correlation or autocorrelation is rejected. Therefore,
there exists autocorrelation and there is a need to correct it.
Final Static Model
Prais-Winsten Robust Regression for Corrective Measures
One way to solve autocorrelation is to use Prais-Winsten Robust Regression. The
result of this regression is shown below.
. prais gdpgr gfcfgr, robust
Iteration 0: rho = 0.0000
Iteration 1: rho = 0.3310
Iteration 2: rho = 0.3796
Iteration 3: rho = 0.3859
Iteration 4: rho = 0.3867
Iteration 5: rho = 0.3868
Iteration 6: rho = 0.3868
Iteration 7: rho = 0.3868
Iteration 8: rho = 0.3868
Prais-Winsten AR(1) regression -- iterated estimates
Linear regression Number of obs = 53
F( 1, 51) = 25.74
Prob > F = 0.0000
R-squared = 0.5080
Root MSE = 1.901
------------------------------------------------------------------------------
| Semirobust
gdpgr | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
gfcfgr | .1764056 .0347717 5.07 0.000 .1065986 .2462126
_cons | 3.229319 .4859764 6.65 0.000 2.25368 4.204957
-------------+----------------------------------------------------------------
rho | .3868144
------------------------------------------------------------------------------
Durbin-Watson statistic (original) 1.332861
Durbin-Watson statistic (transformed) 1.918059
Now that the problem of autocorrelation is solved, the results can be used for the
final static model.
Final Static Model
𝑔𝑑𝑝𝑔𝑟 = 3.229319 + 0.1764056(𝑔𝑓𝑐𝑓𝑔𝑟)
The results show that gross fixed capital formation growth is statistically significant
at 1% significance level. In addition, the results show that there is a positive relationship
between gross fixed capital formation growth and GDP growth which means that the
effect of an increase in gross fixed capital formation growth will increase GDP growth by
0.1764056, ceteris paribus. Lastly, the R-squared is 50.80% which shows the goodness
of fit of the model.
DYNAMIC MODELS
General Distributed Lag Model
Initial General Distributed Lag Model
The following are the initial regression of the General Distributed Lag Model and
the CLRM tests.
Initial Regression
. regress gdpgr gfcfgr l1.gfcfgr
Source | SS df MS Number of obs = 52
-------------+------------------------------ F( 2, 49) = 31.35
Model | 266.272143 2 133.136071 Prob > F = 0.0000
Residual | 208.105933 49 4.24705985 R-squared = 0.5613
-------------+------------------------------ Adj R-squared = 0.5434
Total | 474.378076 51 9.30153089 Root MSE = 2.0608
------------------------------------------------------------------------------
gdpgr | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
gfcfgr |
--. | .1987499 .0270498 7.35 0.000 .1443913 .2531084
L1. | .0222847 .0269705 0.83 0.413 -.0319145 .0764838
|
_cons | 2.975012 .3336207 8.92 0.000 2.304576 3.645448
------------------------------------------------------------------------------
Test for Multicollinearity
. vif
Variable | VIF 1/VIF
-------------+----------------------
gfcfgr |
L1. | 1.08 0.925014
--. | 1.08 0.925014
-------------+----------------------
Mean VIF | 1.08
Test for Heteroscedasticity
. hettest
Breusch-Pagan / Cook-Weisberg test for heteroskedasticity
Ho: Constant variance
Variables: fitted values of gdpgr
chi2(1) = 1.35
Prob > chi2 = 0.2456
Test for Autocorrelation
. bgodfrey
Breusch-Godfrey LM test for autocorrelation
---------------------------------------------------------------------------
lags(p) | chi2 df Prob > chi2
-------------+-------------------------------------------------------------
1 | 6.753 1 0.0094
---------------------------------------------------------------------------
H0: no serial correlation
It can be seen that the null hypothesis that there is no serial correlation will be
rejected since the p-value that was generated from the Breusch-Godfrey test for
autocorrelation (0.0094) is less than 0.05. Therefore, there is autocorrelation and it should
be corrected.
Prais-Winsten Robust Regression for Corrective Measures
. prais gdpgr gfcfgr l1.gfcfgr, robust
Iteration 0: rho = 0.0000
Iteration 1: rho = 0.3475
Iteration 2: rho = 0.3724
Iteration 3: rho = 0.3743
Iteration 4: rho = 0.3744
Iteration 5: rho = 0.3745
Iteration 6: rho = 0.3745
Prais-Winsten AR(1) regression -- iterated estimates
Linear regression Number of obs = 52
F( 2, 49) = 13.00
Prob > F = 0.0000
R-squared = 0.5148
Root MSE = 1.9202
------------------------------------------------------------------------------
| Semirobust
gdpgr | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
gfcfgr |
--. | .1803885 .0353781 5.10 0.000 .1092936 .2514833
L1. | .0209369 .0288574 0.73 0.472 -.0370542 .0789281
|
_cons | 3.122936 .5023444 6.22 0.000 2.113438 4.132435
-------------+----------------------------------------------------------------
rho | .3744517
------------------------------------------------------------------------------
Durbin-Watson statistic (original) 1.274561
Durbin-Watson statistic (transformed) 1.895176
Now that the problem of autocorrelation is corrected, the results can now be used
for the final General Distributed Lag Model.
Final General Distributed Lag Model
After the corrective measure using the Prais-Winsten Robust Regression, the final
General Distributed Lag Model is
𝑔𝑑𝑝𝑔𝑟𝑡 = 3.122936 + 0.1803885(𝑔𝑓𝑐𝑓𝑔𝑟𝑡) + 0.0209369(𝑔𝑓𝑐𝑓𝑔𝑟𝑡−1)
The final General Distributed Lag Model has an optimal lag of 1 as shown in the
Hendry top-down approach and the Alt and Tinbergen approach. The results show that
as the current gross fixed capital growth increases by 1%, current GDP growth also
increases by 0.1803885%, ceteris paribus. In addition, although the past gross fixed
capital formation growth is insignificant, its coefficient is in accordance with the a-priori
expectation. Thus, as the past gross fixed capital formation growth increases by 1%, the
current GDP growth also increases by 0.0209369%. Furthermore, its R-squared is
51.48% which means that the goodness of fit of the final General Distributed Lag Model
is better than the static model.
Koyck Infinite Distributed Lag Model
The Koyck Model has an assumption that there is a “main beta” called the impact
multiplier that decreases geometrically with the lambda lag as time passes by. In simple
words, it assumes that the policy variable from the past has an effect to the current value
of the dependent variable. According to Rufino (2008), this model has a good reputation
because of the idea that the effect of the policy variable is greatest at the year that it is
implemented while it continuously declines as years go by. The effect of the policy
variable expands infinitely which makes it an infinite distributed lag model. Furthermore,
the model is an autoregressive model because the lagged dependent variable is on the
right-hand side of the equation.
There are two ways to estimate the model. One is by using Ordinary Least Squares
estimation. The other is by using Two-Stage Least Squares estimation. The Koyck model
that will use OLS estimation will be written as:
𝑔𝑑𝑝𝑔𝑟𝑡 = 𝛼(1 − 𝜆) + 𝛽0(𝑔𝑓𝑐𝑓𝑔𝑟𝑡) + 𝜆(𝑔𝑓𝑐𝑓𝑔𝑟𝑡) + (𝑢𝑡 − 𝜆𝑢𝑡−1)
OLS Estimation
. regress gdpgr gfcfgr l1.gdpgr
Source | SS df MS Number of obs = 52
-------------+------------------------------ F( 2, 49) = 37.23
Model | 286.098169 2 143.049084 Prob > F = 0.0000
Residual | 188.279907 49 3.84244708 R-squared = 0.6031
-------------+------------------------------ Adj R-squared = 0.5869
Total | 474.378076 51 9.30153089 Root MSE = 1.9602
------------------------------------------------------------------------------
gdpgr | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
gfcfgr | .1802705 .0267331 6.74 0.000 .1265483 .2339928
|
gdpgr |
L1. | .238248 .0979662 2.43 0.019 .0413776 .4351184
|
_cons | 2.211521 .4614323 4.79 0.000 1.284238 3.138804
------------------------------------------------------------------------------
Test for Multicollinearity
. vif
Variable | VIF 1/VIF
-------------+----------------------
gdpgr |
L1. | 1.17 0.856830
gfcfgr | 1.17 0.856830
-------------+----------------------
Mean VIF | 1.17
Test for Heteroscedasticity
. hettest
Breusch-Pagan / Cook-Weisberg test for heteroskedasticity
Ho: Constant variance
Variables: fitted values of gdpgr
chi2(1) = 0.89
Prob > chi2 = 0.3456
Test for Autocorrelation
. bgodfrey
Breusch-Godfrey LM test for autocorrelation
---------------------------------------------------------------------------
lags(p) | chi2 df Prob > chi2
-------------+-------------------------------------------------------------
1 | 2.503 1 0.1136
---------------------------------------------------------------------------
H0: no serial correlation
Final Koyck Infinite Distributed Lag Model Using OLS 𝑔𝑑𝑝𝑔𝑟𝑡 = 2.11521 + 0.1802705(𝑔𝑓𝑐𝑓𝑔𝑟𝑡) + 0.238248(𝑔𝑑𝑝𝑔𝑟𝑡−1)
The initial regression did not violate multicollinearity, homoscedasticity and non-
autocorrelation assumptions which is why the results of the OLS initial estimation will be
used for the final Koyck Infinite Distributed Lag Model. The coefficients of the Koyck model
are all significant and in accordance with the a-priori expectations. The impact multiplier
is .1802705. On the other hand, the rate of decay is .238248. Therefore, a percent
increase in gross fixed capital formation growth will lead to a 0.1802705% increase in
current GDP growth. In addition, a percent increase in the past year’s GDP growth will
lead to a 0.238248% increase in the current GDP growth. Lastly, the goodness of fit of
the model is 60.31%
It must be noted that the results cannot be used for the conclusion because the
lagged GDP growth is endogenous which violates the exogeneity assumption of CLRM.
Thus, these results are biased and inconsistent.
For Koyck models, there are other values that can be interpreted. These are mean
lag, median lag, alpha and the long run multiplier. The computations for these are shown
below.
Alpha = 𝛼(1 − 𝜆)
= 𝛼(1 −.238248) = 2.211521
= 𝛼 = 2.9032034
Mean lag = 𝜆
1−𝜆
= 0.238348
1−0.238248= 0.3127632
Median lag = −𝑙𝑜𝑔2
𝑙𝑜𝑔𝜆=
𝑙𝑜𝑔2
log(0.238248)= 0.4832169
Long-run multiplier = 𝛽 =𝛽0
1−𝜆=
.0267331
1−.0.238248= 0.03509423
The OLS estimates will be used for the Distributed Lag Model written below which
can be interpreted as the effect of gross fixed capital formation growth increases GDP
growth by 0.03409423 of the increase gross fixed capital formation.
𝑔𝑑𝑝𝑔𝑟𝑡 = 𝛼 + 𝛽𝑔𝑓𝑐𝑓𝑔𝑟𝑡 + 𝑢𝑡
𝑔𝑑𝑝𝑔𝑟𝑡 = 2.9032034 + 0.03409423𝑔𝑓𝑐𝑓𝑔𝑟𝑡
Two-Stage Least Squares (2SLS) Estimation
As previously seen from the OLS estimation, there is high R-squared that suggests
the goodness of fit of the model. Furthermore, the OLS estimation shows that the current
gross fixed capital formation growth and the lagged GDP growth are significant and
intuitive. However, because of the possibility of endogeneity in the right-hand side of the
equation due to the inclusion of the lagged GDP growth as an independent variable, then
it means that the assumption of exogeneity in CLRM must have been violated which will
lead to spurious results since the estimates will become biased and inconsistent.
Therefore, this issue should be addressed. In order to address the problem of
endogeneity, Two-Stage Least Squares (2SLS) estimation will be used by using an
instrumental variable to replace the endogenous lagged dependent variable in the right-
hand side of the equation.
Shown below are the initial 2SLS regression and the test for autocorrelation.
. ivreg gdpgr gfcfgr (l1.gdpgr=gfcfgr l1.gfcfgr), first
First-stage regressions
-----------------------
Source | SS df MS Number of obs = 52
-------------+------------------------------ F( 2, 49) = 34.87
Model | 274.431837 2 137.215919 Prob > F = 0.0000
Residual | 192.830531 49 3.93531696 R-squared = 0.5873
-------------+------------------------------ Adj R-squared = 0.5705
Total | 467.262369 51 9.16200723 Root MSE = 1.9838
------------------------------------------------------------------------------
L.gdpgr | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
gfcfgr |
--. | .051473 .0260381 1.98 0.054 -.0008525 .1037985
L1. | .1885336 .0259617 7.26 0.000 .1363615 .2407057
|
_cons | 2.837465 .3211432 8.84 0.000 2.192104 3.482826
------------------------------------------------------------------------------
Instrumental variables (2SLS) regression
Source | SS df MS Number of obs = 52
-------------+------------------------------ F( 2, 49) = 33.62
Model | 280.328307 2 140.164153 Prob > F = 0.0000
Residual | 194.049769 49 3.96019936 R-squared = 0.5909
-------------+------------------------------ Adj R-squared = 0.5742
Total | 474.378076 51 9.30153089 Root MSE = 1.99
------------------------------------------------------------------------------
gdpgr | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
gdpgr |
L1. | .1182 .1381382 0.86 0.396 -.1593991 .3957991
|
gfcfgr | .1926658 .0288885 6.67 0.000 .1346122 .2507193
_cons | 2.639624 .5799338 4.55 0.000 1.474203 3.805044
------------------------------------------------------------------------------
Instrumented: L.gdpgr
Instruments: gfcfgr L.gfcfgr
------------------------------------------------------------------------------
Test for Autocorrelation
. dwstat
Durbin-Watson d-statistic( 3, 52) = 1.447762
The d-statistic is equal to 1.447762. Because it is closer to 2 than 0, then there is
no autocorrelation. Therefore, the initial 2SLS regression results can be used for the final
Koyck Infinite Distributed Lag Model.
Final Koyck Infinite Distributed Lag Model Using 2SLS
𝑔𝑑𝑝𝑔𝑟𝑡 = 2.639624 + 0.1926658(𝑔𝑓𝑐𝑓𝑔𝑟𝑡) + 0.1182(𝑔𝑑𝑝𝑔𝑟𝑡−1)
The final Koyck Infinite Distributed Lag Model that was estimated
using 2SLS now has the best linear unbiased estimates (BLUE)
because it does not violate the assumptions CLRM. Given the regression
results, the impact multiplier is 0.1926658 while the rate of decay is 0.1182.
It can also be seen that the lagged GDP growth is insignificant, its coefficient
is consistent with the a-priori expectation that it positively affects the current
GDP growth. Therefore, a percent increase in gross fixed capital formation
growth will increase the current GDP growth by 0.1926658% while a percent
increase in the lagged GDP growth will increase the current GDP growth by
0.1182%, ceteris paribus.
Alpha = 𝛼(1 − 𝜆)
= 𝛼(1 −0.1182) = 2.639624
= 𝛼 = 2.99344976
Mean lag = 𝜆
1−𝜆
= 0.1182
1−0.1182= 0.134044
Median lag = −𝑙𝑜𝑔2
𝑙𝑜𝑔𝜆=
𝑙𝑜𝑔2
log(0.1182)= 0.3246018
Long-run multiplier = 𝛽 =𝛽0
1−𝜆=
0.1926658
1−0.1182= 0.21849149
The long-run equation of the Koyck Distributed Lag Model that was estimated
using 2SLS is shown below. It can be said that effect of the increase in gross fixed
capital formation growth increases GDP growth by 0.21849149 of the increase in
gross fixed capital formation. The long-run equations are not evaluated for the
standard errors and significance.
𝑔𝑑𝑝𝑔𝑟𝑡 = 𝛼 + 𝛽𝑔𝑓𝑐𝑓𝑔𝑟𝑡 + 𝑢𝑡
𝑔𝑑𝑝𝑔𝑟𝑡 = 2.99344976 + 0.21849149𝑔𝑓𝑐𝑓𝑔𝑟𝑡
Almon Polynomial Distributed Lag (PDL) Model
The Koyck model has coefficients the geometrically decreases as the number of
lags increase which makes it restrictive. Given this and that the restrictions are valid, the
estimates become more efficient but biased and inconsistent if the restrictions are invalid.
To avoid this issue, Almon Polynomial Distributed Lag Model may be used. This model
assumes that the optimal number of lags and the polynomial degree are arbitrarily chosen
(Rufino, 2008).
In this model, the lagged values of the independent variable are located on the
right-hand side of the equation. Given that the Hendry top-down approach showed that
the optimal lag should be 1, then it will be used.
Initial Regression
. regress gdpgr gfcfgr l1.gfcfgr
Source | SS df MS Number of obs = 52
-------------+------------------------------ F( 2, 49) = 31.35
Model | 266.272143 2 133.136071 Prob > F = 0.0000
Residual | 208.105933 49 4.24705985 R-squared = 0.5613
-------------+------------------------------ Adj R-squared = 0.5434
Total | 474.378076 51 9.30153089 Root MSE = 2.0608
------------------------------------------------------------------------------
gdpgr | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
gfcfgr |
--. | .1987499 .0270498 7.35 0.000 .1443913 .2531084
L1. | .0222847 .0269705 0.83 0.413 -.0319145 .0764838
|
_cons | 2.975012 .3336207 8.92 0.000 2.304576 3.645448
------------------------------------------------------------------------------
Test for Multicollinearity . vif
Variable | VIF 1/VIF
-------------+----------------------
gfcfgr |
L1. | 1.08 0.925014
--. | 1.08 0.925014
-------------+----------------------
Mean VIF | 1.08
Test for Heteroscedasticity
. hettest
Breusch-Pagan / Cook-Weisberg test for heteroskedasticity
Ho: Constant variance
Variables: fitted values of gdpgr
chi2(1) = 1.35
Prob > chi2 = 0.2456
Test for Autocorrelation . bgodfrey
Breusch-Godfrey LM test for autocorrelation
---------------------------------------------------------------------------
lags(p) | chi2 df Prob > chi2
-------------+-------------------------------------------------------------
1 | 6.753 1 0.0094
---------------------------------------------------------------------------
H0: no serial correlation
Prais-Winsten Robust Regression for Corrective Measures . prais gdpgr gfcfgr l1.gfcfgr, robust
Iteration 0: rho = 0.0000
Iteration 1: rho = 0.3475
Iteration 2: rho = 0.3724
Iteration 3: rho = 0.3743
Iteration 4: rho = 0.3744
Iteration 5: rho = 0.3745
Iteration 6: rho = 0.3745
Prais-Winsten AR(1) regression -- iterated estimates
Linear regression Number of obs = 52
F( 2, 49) = 13.00
Prob > F = 0.0000
R-squared = 0.5148
Root MSE = 1.9202
------------------------------------------------------------------------------
| Semirobust
gdpgr | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
gfcfgr |
--. | .1803885 .0353781 5.10 0.000 .1092936 .2514833
L1. | .0209369 .0288574 0.73 0.472 -.0370542 .0789281
|
_cons | 3.122936 .5023444 6.22 0.000 2.113438 4.132435
-------------+----------------------------------------------------------------
rho | .3744517
------------------------------------------------------------------------------
Durbin-Watson statistic (original) 1.274561
Durbin-Watson statistic (transformed) 1.895176
Now that the model has undergone the necessary corrective measure, the results
from the Prais-Winsten Robust Regression can now be used for the final Almon
Polynomial Distributed Lag Model.
Final Almon Polynomial Distributed Lag Model 𝑔𝑑𝑝𝑔𝑟𝑡 = 3.122936 + 0.1803885(𝑔𝑓𝑐𝑓𝑔𝑟)𝑡 + 0.0209369(𝑔𝑓𝑐𝑓𝑔𝑟)𝑡−1
It can be seen that the current and the lagged gross fixed capital formation growth
positively affects the current GDP growth. Although the p-value of the lagged gross fixed
capital formation growth is 0.472 is greater than 0.05 which makes the variable
insignificant, its coefficient is consistent with the a-priori expectation. Thus, a percent
increase in the current gross fixed capital formation and lagged gross fixed capital
formation growth will increase the current GDP growth by 0.1803885% and 0.0209369%,
respectively. In addition, it has an R-squared of 51.48% which represents the goodness
of fit of the model.
Autoregressive Distributed Lag Model (ARDL)
After determining the results of AR and DL models, what will be determined now
is the combination of the two, called the ARDL model. In this model, the dependent and
independent variables are lagged. Because the Hendry top-down approach and Alt and
Tinbergen estimation resulted to having 1 as the optimal number of lag, then it will be
employed in this model.
Initial Regression
. regress gdpgr gfcfgr l1.gfcfgr l1.gdpgr
Source | SS df MS Number of obs = 52
-------------+------------------------------ F( 3, 48) = 25.69
Model | 292.307989 3 97.4359962 Prob > F = 0.0000
Residual | 182.070087 48 3.79312682 R-squared = 0.6162
-------------+------------------------------ Adj R-squared = 0.5922
Total | 474.378076 51 9.30153089 Root MSE = 1.9476
------------------------------------------------------------------------------
gdpgr | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
gfcfgr |
--. | .1798361 .0265632 6.77 0.000 .1264273 .233245
L1. | -.0469919 .0367268 -1.28 0.207 -.120836 .0268522
|
gdpgr |
L1. | .3674497 .1402526 2.62 0.012 .0854531 .6494464
|
_cons | 1.932386 .5077205 3.81 0.000 .9115458 2.953227
------------------------------------------------------------------------------
Test for Multicollinearity
. vif
Variable | VIF 1/VIF
-------------+----------------------
gdpgr |
L1. | 2.42 0.412681
gfcfgr |
L1. | 2.24 0.445521
--. | 1.17 0.856690
-------------+----------------------
Mean VIF | 1.95
Test for Heteroscedasticity
. hettest
Breusch-Pagan / Cook-Weisberg test for heteroskedasticity
Ho: Constant variance
Variables: fitted values of gdpgr
chi2(1) = 0.46
Prob > chi2 = 0.4972
Test for Autocorrelation
. bgodfrey
Breusch-Godfrey LM test for autocorrelation
---------------------------------------------------------------------------
lags(p) | chi2 df Prob > chi2
-------------+-------------------------------------------------------------
1 | 1.084 1 0.2979
---------------------------------------------------------------------------
H0: no serial correlation
Final Autoregressive Distributed Lag Model
Because the initial regression did not violate the tests for the CLRM assumptions,
then its results can be used for the final Autoregressive Distributed Lag Model. Thus, the
final model is:
𝑔𝑑𝑝𝑔𝑟𝑡 = 1.932386 + 0.1798361(𝑔𝑓𝑐𝑓𝑔𝑟)𝑡 − 0.0469919(𝑔𝑓𝑐𝑓𝑔𝑟)𝑡−1
+ 0.3674497(𝑔𝑑𝑝𝑔𝑟)𝑡−1
The results show that the current gross fixed capital formation growth and the
lagged GDP growth have significant relationship to the current GDP growth. However,
this is not the case for the lagged gross fixed capital formation growth. To interpret the
results, a percent increase in the current gross fixed capital formation growth will increase
GDP growth by 0.1798361% and a percent increase in the lagged GDP growth will
increase the current GDP by 0.3674497%. In addition, the model has an R-square which
is equal to 61.62% which represents the goodness of fit.
CONCLUSIONS AND RECOMMENDATIONS
The significance of this paper was shown through determining the effect of gross
fixed capital formation growth on GDP growth. After using various dynamic models such
General Distributed Lag Model, Koyck Infinite Distributed Lag Model estimated through
OLS and 2SLS and Autoregressive Distributed Lag Model, the results showed that the
current value of the gross fixed capital formation growth really has a positive
relationship with GDP growth. However, the result regarding the effect of the lagged
gross fixed capital formation growth is ambiguous because it is only significant in the
Almon Polynomial Distributed Lag Model. In addition, the lagged GDP growth also
poses ambiguous results because it is only significant at the Autoregressive Distributed
Lag Model and the Koyck Infinite Distributed Lag Model estimated using OLS.
The result that gross fixed capital formation growth positively affects GDP growth
but does nog Granger-cause GDP growth is consistent with most empirical literature.
One of which is the study of Blomstrom, Zejan and Lipsey (1993) that determined
causality through using five-year periods after the World War II. In the said study, it was
concluded that “fixed capital formation is not the key to economic growth.”
For future researches regarding this topic, it is suggested that the number of
observations may be increased since it may cause changes in the methodology since
unit roots and lags may change. Another recommendation is the use of another
functional form which may yield more meaning results.
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