Seminar on Registers in Statistics - methodology and quality21 - 23 May, 2007 Helsinki

Montserrat Herrador and Juana PorrasINSTITUTO NACIONAL DE ESTADISTICA, SPAIN

The use of administrative register toThe use of administrative register toimprove sampling frame. Experiencesimprove sampling frame. Experiencesand possibilities in Spain.and possibilities in Spain.

◆◆ I. Introduction.I. Introduction.

◆◆ II. Population Census in the constructionII. Population Census in the constructionof the frame.of the frame.

◆◆ III. Spanish population register:UsefulIII. Spanish population register:Usefuladministrative information in theadministrative information in theconstruction of the population frame.construction of the population frame.

◆◆ IV. Combination of administrative recordsIV. Combination of administrative recordsand their use in sample design.and their use in sample design.

◆◆ V. Conclusions.V. Conclusions.

■■ I. INTRODUCTIONI. INTRODUCTION

◆◆ Sampling frame is fundamental in a survey.Sampling frame is fundamental in a survey.

◆◆ The frame is the list of units from where theThe frame is the list of units from where thesample is selected.sample is selected.

◆◆ Additional available information is necessaryAdditional available information is necessaryto improve the efficiency of sample design:to improve the efficiency of sample design:

✦ Stratification variables.✦ Probabilities of sample selection.✦ Carry out the fieldwork.

■■ In any guidelines for frames, two relevantIn any guidelines for frames, two relevantaspect are includedaspect are included::◆◆ The construction: which sources?The construction: which sources?◆◆ Maintenance: which procedures?Maintenance: which procedures?

■■ For households surveys INE uses aFor households surveys INE uses adouble frame formed by:double frame formed by:◆◆ First stage sampling units:First stage sampling units:

✦ Census section:500-3000 inhabitants◆◆ Second stage sampling units:Second stage sampling units:

✦ Dwellings

■■ Traditionally INE has constructed theTraditionally INE has constructed theframe on the basis of Censusframe on the basis of Census..

◆◆ About 3000 census sections were selectedAbout 3000 census sections were selectedfrom Census in order to be used in all thefrom Census in order to be used in all thehousehold surveys carried out by INE.household surveys carried out by INE.

◆◆ The frame of PSU�s and The frame of PSU�s and SSU�s SSU�s has beenhas beenperiodically updated.periodically updated.

■■ Nowadays, for most household surveys,Nowadays, for most household surveys,the frame is constructed from thethe frame is constructed from theSpanish Population Register.Spanish Population Register.

■■ II. Population census in the constructionII. Population census in the constructionof the frame.of the frame.◆◆ Census is the only source that:Census is the only source that:

✦ Provide auxiliary information for the PSU�s.✦ Prepare the list of dwellings from which the

sample is selected.

◆◆ T The quality in the auxiliary information ,especially in variables correlated with thestudy variables, improve the efficiency ofsampling designs

✦ Stratification and substratification.✦ Application of Calibration Techniques in the

estimators.

◆◆ Stratification process is performedStratification process is performedaccording to the size of the municipalityaccording to the size of the municipalitywhich the census section belongs to.which the census section belongs to.

◆◆ Sub-stratification process make use of Sub-stratification process make use ofthe following variables:the following variables:

✦ Activity status✦ Occupation and branch of activity✦ Nationality (proportion of foreigners)✦ Highest level of education completed✦ Age and sex groups✦ Socio-economic condition✦ Income variables

CPRO CMUN DIST NSECC Population % 0-19 years

% 15-24 years

% 65 and over years

% unemployed persons

% inactive persons

% employed persons

% foreigners

41 091 01 022 1.146 9,34 21,29 20,24 10,38 53,66 35,95 3,1441 091 01 023 1.487 9,75 21,52 16,75 11,97 49,83 37,26 2,6941 091 01 024 1.261 10,55 17,76 20,38 10,47 54,48 34,66 2,3841 091 01 025 2.036 11,25 19,40 17,58 9,48 49,85 37,28 2,6541 091 01 027 1.391 9,99 22,00 21,21 5,97 54,57 39,47 1,0141 091 01 028 773 12,55 20,83 17,21 11,25 52,65 34,67 2,8541 091 01 029 1.915 9,92 23,86 13,68 11,96 47,42 35,67 1,0441 091 01 030 762 8,27 23,23 22,18 6,96 53,67 37,53 0,7941 091 01 031 758 8,84 17,81 26,65 10,16 56,20 33,64 1,72

CPRO CMUN DIST Nº SECC lowest medium highest

Overall income per dwelling with recipients

% unemployment benefits income

% Properties income

% Farm income Subestratum

41 091 01 022 39,70 37,87 22,43 19160,6 2,0 4,6 0,1 441 091 01 023 36,85 42,57 19,64 17464,7 2,2 3,1 0,0 441 091 01 024 44,96 33,23 21,41 19662,2 1,6 5,2 0,3 441 091 01 025 43,71 34,33 18,57 18711,8 1,8 3,7 0,3 441 091 01 027 26,82 37,60 35,59 44987,0 0,5 23,4 1,2 641 091 01 028 46,18 33,12 19,28 19579,7 1,5 4,6 0,4 441 091 01 029 37,08 39,95 18,02 19480,2 1,7 4,6 0,3 441 091 01 030 29,27 43,96 24,93 33633,7 1,2 6,6 0,0 441 091 01 031 41,29 39,58 19,13 17857,5 2,7 4,1 0,1 4

% persons with level of studies

◆◆ Second stage frameSecond stage frame::

✦ Made up of family dwellings classified inthe census as occupied or empty, but onlythe first one are selected.

✦ Updating consists of visiting emptydwellings and any other census unit,(business premises, newly built dwellings,etc.), to see whether their situation haschanged and, if so, include it in the frame.

✦ This updating process is carried out everyyear and a half.

■■ III. The Spanish Population Register(SPR): UsefulIII. The Spanish Population Register(SPR): Usefuladministrative information for the construction ofadministrative information for the construction ofthe population frame.the population frame.

◆ The SPR is the administrative record in which theresidents of the municipality are set down.

◆ Its data provide evidence of residence in themunicipality and of having permanent addressthere.

◆ The SPR is governed by Law 4/1996, of 10 January,regulating the Basis of Local Government, inrelation to the Municipal Register.

◆ It is regulatory development, approved by RoyalDecree 2612/1996, of 20 December, amending theold Regulations on Population and TerritorialDemarcation of Local Authorities..

◆ Article 16.3 of Law 4/1996 regulate the use of theRegister for statistical purposes.

◆ The Local Council is responsible for itsconstruction, maintenance, review and safekeeping.

◆ Previously the register was reviewed in the yearsending in 1 and 6, now it is maintained updatedcontinuously.

◆ The opportunity of using this register for statisticalpurposes has provided the possibility of having anew alternative source to construct the samplingframe for household survey.

◆ Two types of surveys aimed at the population arecarried out by INE:

✦ Continuous Surveys✦ Structural Surveys.

◆ For the moment, INE uses the SPR as a samplingframe only for structural surveys.

◆ The SPR is the list of inhabitants in Spain, whichpermits its use both as:

✦ a frame of persons.✦ a frame of dwellings.

This utilisation consists of obtaining dwellings as a setof persons registered at the same postal address.

◆ Being a live record of the population, its mainadvantages is that it makes a permanently updatedframe of areas available quickly and economically, onwhich the two-stage sampling design ,used in the INEhousehold surveys, can be applied.

■■ Problems with the use of the SPR.Problems with the use of the SPR.

◆◆ Obtain dwellings raises difficulties due to the Obtain dwellings raises difficulties due to the lack ofstandardisation in the postal addresses and errors and errorsin the processing of municipal register page numbering.in the processing of municipal register page numbering.

◆◆ Being a public document, offers Being a public document, offers limited auxiliarylimited auxiliaryinformation.information.

◆ Selection of misclassify dwellings. On one hand,dwellings classified as principal ones are in fact emptydwellings and,on the other hand, persons whotheoretically are living in these misclassify dwellings, donot have probability of being selected.

■■ IV. Combination of administrative records andIV. Combination of administrative records andtheir uses in sample designtheir uses in sample design..

✦ INE and AEAT (Tax Agency) have a stableframework of cooperation in the scope ofinformation exchange for statistical and taxationpurposes.

✦ AEAT supplies to INE aggregated tax informationfor different types of territorial units, the smallestlevel that supplied is census section , the primarysampling unit in household surveys.

✦ The aggregated tax information is obtainedmatching the information from SPR to the AEATfile by the use of the ID Card Number of thepersons registered in the SPR.

✦ The main aim is to obtain a classification of censussections according to the level and structure ofdeclared income, aggregated for all the residents inthe section.

✦ The INE experience in the utilisation of theinformation from AEAT :

� Substratification of the primary sampling units in the framefor household surveys. Different income level variables wereused as substratification variables for the new sample designs ofthe LFS 2005 and the Household Budget Survey 2006.

� Sampling design of the Family Financial Survey, carried outby the Bank of Spain in 2002 and 2005.

✦ The structure of income indicators presentcorrelation with a wide variety of socialcharacteristics of the households that are studied inofficial INE surveys.

■■ V. ConclusionsV. Conclusions◆◆ SPR has allowed the possibility of using an

alternative updated sampling frame, althoughrequiring adaptations for its statistical use.

◆ The use of auxiliary information from administrativesources enables the improvement of the efficiencyon household surveys, for example the use of taxinformation from AEAT.

◆ In order to improve the use of the administrativeregister, INE is developing a new project namedLongitudinal Demographic Study (EDL).

■■ VI.What is the EDL project?VI.What is the EDL project?◆ The main goal of this project is to create a data base

to collect longitudinal information on all the people,households, dwellings, etc. using the SPR as a pivot.

◆ The EDL will manage to match different administrativesources.

◆ EDL objectives:✦ To provide demographic longitudinal information.✦ To offer an instrument of co-ordination and

harmonisation from different sources.✦ To offer an optimal sampling frame for population

surveys.✦ To create the infrastructure in the operation of the

Demographic Census 2011 and so on.