Transcript
Page 1: The demographic effect of mixed marriages

European Journat of Population 4 (1988) 145-156 145 North-Holland

THE DEMOGRAPHIC EFFECT OF MIXED MARRIAGES

Fjalar FINNAS * ~4bo Akademi, Vasa, Finland

Received September 1988, final version received November 1988

Abstract. This paper gives a formal expression for the demographic effect of mixed marriages; i.e., the effect on the number of children, and thereafter illustrates the long-term effects of these marriages with a simple simulation model

Rdsumd. L 'effet ddmographique des mariages mixtes Cet article formalise l'effet d6mographique des mariages mixtes, c'est-~-dire leur effet sur le nombre d'enfants, et illustre ensuite l'effet h long terme de ces mariages en utilisant un mod61e simple de simulation.

1. Introduction

SociM scientists have shown great interest in the study of different kinds of mixed marriages. The frequency of mixed marriages has often been considered to be the most conclusive and objective indicator of the degree of assimilation of a minority (see, e.g., Mittelbach and Moore (1968)). Mixed marriages are of great interest f rom a demo- graphic point of view, too, but so far very little research has been done in this respect.

Unless one of the two spouses joins the group to which his or her partner belongs (this is possible for example in religious groups), a mixed marriage does not by itself have any direct effect on population size. The demographic effect of the mixed marriage appears in the generations which follow, mainly via the classification of the children of such marriages into subpopulations. In the case of language groups this classification is not necessarily predetermined. In this paper, I will first derive a formal expression for the demographic effect of mixed

* Author's" address: Social Science Research Unit, Vasaesplanaden 15B, SF-65100 Vasa, Finland.

0168-6577/88/$3.50 © 1988, Elsevier Science Publishers B.V. (North-Holland)

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marriages i.e., the effect on the number of children, and thereafter illustrate the long-term effects of these marriages with a simple simula- tion model.

2. The first-generation effect

In what follows I will ignore classification problems. Further, I will consider only populations in which all individuals can unequivocally be classified according to a given variable - such as religion, citizenship, race or language. In principle the number of groups involved could be more than two, but for the sake of simplicity and clarity I shall include only two subpopulations. Transitions between the two groups are allowed but, at any given time, the classification is presumed to be (and is kept) always unequivocal. To make the presentation easier, I shall deal with the following two language groups: Finnish and Swedish.

Assume that we study a closed cohort; that the fertility of this cohort is independent of its linguistic composition, and that the proportion of its members getting married is the same regardless of the existence or non-existence of mixed marriages. The number of males and females is assumed to be equal, and there are no differences between the sexes in any respect. The children of mixed marriages could belong to either language group, but in the case of unilingual marriages they are assumed to have the same language as their parents. If there are language shifts between the different groups, they are assumed to take place at the moment of marriage. After a language shift of one of the spouses, the new homogeneous marriage is considered to be no differ- ent from the originally unilingual ones.

To study the effect of mixed marriages under the assumptions noted above, we have to keep track of the marriages that remain mixed, the language of the children in these marriages, and the frequency of the language shifts involved together with their direction. Given the fairly well-known result that the frequency of mixed marriages in a subpopu- lation is to a great extent determined by the relative size of the subpopulation (see e.g. Blau (1977)) we think it necessary to study the effect of relative subpopulation size in differing situations. From the study of the Swedish population in Finland it is also evident that the other factors may depend on the linguistic composition of the popula- tion. I shall introduce the following notations, where x (0 < x < 1) is the proportion of Swedes in the population:

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n~ = the proportion (among all Swedes who marry) of Swedish per- sons marrying Finns,

G = the proportion of the children who are Swedish in mixed mar- riages that remain mixed,

kx = the proportion of mixed marriages in which one of the spouses shifts to the language group of the other,

w~ = the proportion of language shifts directed from the Finnish to the Swedish language group.

To study the effect of mixed marriages we have to compare the number of children in a cohort where mixed marriages occur, with one in which only unilingual marriages take place. In the latter case the number of Swedish children, Sbo(X), can be expressed as

Sb o (x) = c lc2 x,

where c 1 and c 2 are constants representing the total number of marriages taking place and the number of children per marriage, respectively.

Since the total number of marriages is Cl, the number of Swedish males as well as females getting married is ClX. Under the assumptions made, qxn~ of both sexes will marry a Finnish partner resulting in a total of 2qxn~ mixed marriages and q x ( 1 - nx) unilingual Swedish ones. Out of the mixed marriages, 2 q x n x k ~ become unilingual as a result of language shifts, 2clxn~kxw ~ become unilingual Swedish and 2cxxn:~k~ ( 1 - wx) unilingual Finnish. The number of unilingual Swedish and mixed marriages are therefore qx(1 - n~) + 2Caxn~k~w x and 2qxnx (1 - k~), respectively.

If mixed marriages occur, the total number of Swedish children is therefore

S b l ( X ) = ClC2X((1 -- nx) + 2nxkxw~ + 2n~(1 - k x ) G ) .

The effect of mixed marriages, i.e., the relative change in the number of Swedish children, is then

d ( x ) = S b a ( x ) - Sb°(x) Sbo(x) = n ~ ( k x ( Z w ~ - l ) + ( 1 - k ~ ) ( Z G - 1 ) ) •

In any given population we have to estimate the values of the functions n:~, kx, wx and G to calculate the expression for d(x). If we

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T a b l e 1

T h e r e l a t i v e e f f e c t o f m i x e d m a r r i a g e s o n t h e n u m b e r o f S w e d i s h c h i l d r e n u n d e r d i f f e r e n t

l i n g u i s t i c c o n d i t i o n s w i t h v x = (1 + x ) / 3 , w x = (1 + 3 x ) / 5 a n d n ~ = (1 - x ) / 2 .

x k

0.1 0 .2 0 .3 0 .4

0 .05 - 0 .154 - 0 .165 - 0 .177 - 0 .188

0 .10 - 0 .130 - 0 . I 3 9 - 0 .149 - 0 .158

0.25 - 0 .068 - 0 .073 - 0 .078 - 0 .083

0 .50 0 .000 0 .000 0 .000 0 .000

0 .75 0 .023 0 .024 0 .026 0 .028

0 .90 0 .014 0 .015 0 .017 0 .018

0 .95 0 .008 0 .009 0 .009 0 .010

study not just one, but several populations under widely varying conditions, it may be necessary to estimate their entire functional forms. This was the case in the study of the Swedish population in Finland, since the Swedish proportion of the total population varies very much in the different municipalities (Finn~is (1986)). To illustrate the magnitude of the expression d(x), I will now present some calcula- tions for different linguistic situations and varying proportions of language shifts. To make the assumptions about the functions realistic, I have based them on the results from the Finnish study. I assume that the proportion intermarrying is n x - - ( 1 - x ) / 2 ; that a proportion w x --(1 + 3x) /5 of the language shifts is directed from Finnish to Swedish, and that the Swedish proportion of the children in the remaining mixed marriages is v x = (1 + x)/3. The frequency of lan- guage shifts is assumed to be independent of the linguistic conditions, i.e., kx = k. Note that these assumptions imply that the language groups in question are equal in the sense that the outcome is indepen- dent of which group makes up the majority.

Now let us look at the situation where the Swedes are one tenth of the whole population, and there are language shifts in 30 per cent of the originally mixed marriages, i.e., k = 0.3. Under the assumptions made, we then have n0.1 = 0 . 4 5 , i.e., 45 per cent of the Swedes marry Finnish partners, and since v0.1 = 0.367, 36.7 per cent of the children in the remaining mixed marriages becomes Swedish. Further, w0.1 -- 0.26, which means that 26 per cent of the language shifts take place from the Finnish to the Swedish language group. Taken together, the effect of the mixed marriages is a reduction of the number of Swedish children by 14.9 per cent. With language shifts in 40 per cent of the mixed

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marriages, the number of Swedish children is reduced by a total of 15.8 per cent. Out of this total reduction, 7.2 per cent is the result of the marriages that remain bilingual, while the rest, or 8.6 per cent, arise from the marriages in which language shifts among the parents occur. These figures show that if we are interested in the total effect of mixed marriages, and if transitions between the groups are possible, then it is of decisive importance to start from the contracted marriages instead of studying the remaining mixed marriages only.

Although the effect for both groups is of equal size in absolute figures, the relative effect is much smaller for the majority. The reduction of 15.8 per cent mentioned above corresponds to an increase of only 1.8 per cent for the majority. Another result of the shift in favour of the majority is that the Swedish proportion of all children is reduced to 8.4 per cent.

The expression for the total effect presented above is based on a comparison of the number of children in a cohort in which mixed marriages occur with the number in a situation where all the contracted marriages are unilingual. For that reason this effect may be called a first-generation effect. If we regard mixed marriages as part of an assimilation process, it is also interesting to study the effect in a long-term perspective. We should then be aware of the fact that the effect presented above may change from one generation to the next. Note first that even in a closed population, the relative sizes of the subpopulations will probably change, as an effect of the mixed mar- riages. Note also, at least for religious (Thomas (1951)) and language groups (Finn~is (1982)), that persons with a homogeneous background tend to choose their partners more endogamously than do persons with a heterogeneous background. This means that the function nx, intro- duced before, will change in successive generations, and that the effect of mixed marriages will accumulate. One way of studying how the function nx, as well as the total effect d(x), changes is to specify a model for the mating process, and to study consequent developments in successive generations. In the next section, I give a short presentation of such a model and the main results obtained from its use.

3. The long-term effect

The model constructed for the mating process is based on the assumption that all individuals can be classified as 'endogamous' or

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'exogamous' with respect to their behaviour in the mate selection process. 'Exogamous' persons are assumed to select their partners randomly, ignoring the factor of language, while a marriage between two 'endogamous' persons from different groups is taken to be impossi- ble. This means that 'endogamous' persons choose their partners only among persons from their own language group and among 'exogamous' persons from the other one. A much more easily understood descrip- tion is obtained in our case if we replace the terms 'endogamous' and 'exogamous' by 'unilingual' and 'bilingual', respectively, thus taking into account actual ability to use language. The model then implies that mate selection is done randomly as regards language; the combination ' unilingual Swedish' and 'unilingual Finnish' being considered impossi- ble. The process is assumed to be independent of age and sex, and all the persons are assumed to be equally active in the marriage market.

Family background enters the model through the classification of individuals as 'endogamous' or 'exogamous'. I assume that all persons with a heterogeneous background and a certain proportion of those with a homogeneous background are 'exogamous', while the rest of the latter group is 'endogamous'. Further, the division of persons with a homogeneous background into 'endogamous' and 'exogamous' is as- sumed to be dependent on the relative sizes of the subpopulations.

The mate selection process under discussion can also be described mathematically as an urn model with two urns. Assume that we have one urn with blue (men) balls and one with red (women) ones. In both urns the balls have a number, 1, 2, 3 or 4, corresponding to 'endoga- mous Swedish', 'exogamous Swedish', 'exogamous Finnish' and 'endo- gamous Finnish', respectively. For every pair to be formed we first pick an urn at random, and then draw a ball (a 'suitor', who may be a female) from it also at random. From the other urn we draw another ball at random. If the two balls form a forbidden combination (1-4 or 4-1), the latter ball is put back into the urn, and a new ball is drawn from it. We continue until a permitted pair is obtained. This pair of balls is put aside before we start to form a new pair. If it is impossible to find a permitted 'partner' for a given 'suitor', the ball corresponding to the latter has to be put back and we have to draw another one instead. The process terminates when new permitted pairs cannot be formed, or when a predetermined proportion of" the balls has been drawn.

The urn model is simple, though no explicit mathematical expression

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for the expected outcome of the process has yet been found. In principle we can cMculate the expected outcome recursively, but this requires an enormous amount of computer resources in practice. Another and much simpler method is to simulate the process, and that is what I have done.

Although I have simulated the mate selection process in stochastic fashion, all the other calculations measuring the effect of mixed mar- riages are deterministic. I started from the outcome of the process, i.e., the number of marriages (pairs) of different combinations, and as- sumed that the number of children was independent of the linguistic composition of the marriage. Language shifts are permitted, and the language of the children in the remaining mixed marriages is de- termined by a function G. Assuming that children choose partners of their own generation, and that this happens according to the same pattern as their parents, it is possible to study how the effect of mixed marriages changes in successive generations as the result of changes in the composition of the population with respect to family background.

In my own calculations I have started from a cohort in which all persons share the language of their parents. There are no differences between the sexes - neither in behaviour nor in quantity. Looking at the standard deviations I concluded, after some experiments, that a cohort size of 2 000 persons and 100 repetitions of the process would render results reliable enough to my purposes. The calculations were carried out for cohorts with different linguistic compositions. All generations were supposed to have the following characteristics:

- The proportion that marry is 90 per cent. - The proportion of 'exogamous' persons, of those with a homoge-

neous background, is directly proportional to the relative size of the other language group. Denoting this proportion ux, we can write u~ = h ( 1 - x) for the Swedish population. Here h is a parameter, and I have used values for h in the interval 0.1-0.6.

- The Swedish proportion of children in mixed marriages is: G = (1 + x)/3.

- The frequency of language shifts is independent of the linguistic composition of the population, i.e., k x = k . The values for k are in the interval 0.0-0.5.

I have not assumed a certain function w~ for the direction of the language shifts, but my starting point has been the composition of the

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marriages. In a mixed marriage between an 'endogamous' and an 'exogamous' person, it is always the latter person that has made the shift. If both persons are 'exogamous' the proportion of language shifts from the Finnish to the Swedish group is equal to x, i.e., the relative size of the Swedish population.

Before studying the total effect of mixed marriages, let us take a look at the development of their frequency in successive generations. For this purpose, instead of n x, I have used a function px, defined as

- x ) .

The advantage of this function can be seen as follows. If the proportion that marry is the same in both language groups, then we can write

n x x = n l _ x ( 1 - x ) .

This expression merely indicates that the number of mixed marriages is the same in both language groups. Now, if we have n x =Px (1 - x) as above, we also get

n l _ x = px x ,

which means that the function p is a measure that is standardized with respect to the linguistic composition of the population. In fact, the function p is 1 - ~ where ~: is the conditional kappa used by Rust and Seed (1985) for example. The function p can consequently be consid- ered as an indicator of the level of endogamy in the population. The higher the value of the function, the smaller the importance of language in the mate selection process. In a situation where the selection is made at random with respect to language, the expected value of p is one.

One effect of the mating process used here is that the proportion that marries is somewhat lower within the minority than within the majority. The differences are, however, so small that the effect on the function p is almost negligible, and it is not necessary to calculate separate values for p for the two language groups.

On the assumptions made, the function p m fact depends on four variables, all of which have to be considered. These variables are the Swedish proportion in the first generation (x), the generation (g), and the parameters h and k. As expected the value of the function p

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.8 (a)

+I . g - a / + ,2

p(o5, g,03,04)

+2 ,~ .6 .8 ZO • / {c)

T ~Y°s'g'~ ...... ,....~=k = 0 0

2 1 / ~ / p p ( o s, gK0,¢j + + (05, I I,

.2 .~, .6 .8 ZO

Fig. 1. The development of x, k and h,

+8

.6

.4

.2

p(, g 4 03O ~1 • ' / / = 0 1 0

< - ~ = 0.25 (b) .... : : :~ ; -~ /x = 0,5 o

.2 .,4+ ,6 .8 I+0

l p+ s++++,~ ~+ (d)

~h:~

V / . / . .~/ h= 2

J + ~ l , , 2 i h =1

"°':U2'

.2 .4. 6 .8 "ZO

Interpretation. The numbered points in fig. l(a) are the values of the function p in the first five generations. To be able to illustrate several development alternatives in the same figure, a line is drawn through the points. To study the development in detail in figs. l (b ) - l (d ) , a step-function corresponding to that in fig. l(a) should be plotted•

increases from one generation to the succeeding one (fig. l(a)). How- ever, after 4 - 5 generations the increase has decreased and the value of p is almost a constant. The proportions of mixed marriages within a minority still increases somewhat, because its relative size decreases successively, and p(x, g, k, h) is a decreasing function with respect to x (fig. l(b)).

The parameter h has a direct effect on the number of 'exogamous' persons, and the greater this proportion, the more frequent are mixed marriages. Thus the function p(x, g, k, h) is an increasing function with respect to h (cf. fig. l(d)). On the other hand, it is decreasing with respect to k, since an increasing number of language shifts will reduce the number of 'exogamous' persons (fig. 1(c)).

In what follows I shall present a specific case in some detail so as to illustrate the total long-term effect of mixed marriages. In my example,

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Table 2 The expected effect of the mixed marriages on the number of children in five successive generations for a minority that originally is one fourth of the total population, h = 0.4 and k = 0.3. Per cent. ab

Gene- p The effect of mixed marriages (4) (5)

ration (1) (2) (3) Total

1 0.404 (0.0024) - 0.8 - 3,1 - 3.5 - 7.4 (0.17) 18.9 (0.12) 23.1 2 0.587 (0.0030) - 1.0 - 4.6 - 5.6 - 11.2 (0.17) 28.9 (0.16) 20.6 3 0.678 (0.0032) -1 .3 -6 .5 -7 .3 -15.1 (0.19) 35.2 (0.19) 17.4 4 0.718 (0.0037) - 1.4 - 8,3 - 8.8 - 18.5 (0.23) 39.3 (0.24) 14.2 5 0.741 (0.0045) -1 .8 - 9 . 9 -10 .4 -22.1 (0.25) 42.8 (0.33) 11.1

a (1): the effect of a lowered proportion that marry; (2): the effect from originally mixed marriages that become unilingual owing to language shifts among spouses; (3): the effect of the classification of the children in the remaining mixed marriages; (4): the proportion of the minority that has a heterogeneous background; (5): the proportion of the minority of the total

cohort. b The numbers in parentheses are standard errors after 100 simulations

the Swedes constitute a minority of one fourth of the original popula- tion, and the parameters h and k are assumed to have the values h = 0.4 and k = 0.3. The effect in five successive generations is pre- sented in table 2.

The value 0.4 for the parameter h means that in the original cohort 30 per cent of the Swedes and 10 per cent of the Finns were 'exoga- mous' (0.4.0.75 -- 0.30 and 0.4.0.25 = 0.10). If 90 per cent of the total population marry, the expected outcome of the mate selection process is that the corresponding proportions for the Swedes and the Finns are 89.2 and 90.4 per cent, respectively. Out of all the Swedes that marry, 30.3 per cent have a Finnish partner giving the value of 0.404 for the function p. Since we assume that k = 0.3, there are language shifts in 30 per cent of all mixed marriages, and in 33.8 per cent of these cases it is the Finnish spouse who moves to the Swedish group. Since 00.25-- 0.417, 41.7 per cent of the children in the remaining mixed marriages become Swedish. Taken as a whole this means that the expected number of Swedish children is reduced by 7.4 per cent as a result of mixed marriages. The corresponding relative gain for the Finns is 2.5 per cent. Note that of all the Swedish children, 18.9 per cent have a heterogeneous background.

In the succeeding generations the expected value of the function p increases via 0.587, 0.678 and 0.718 to 0.741. This, in combination with

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Table 3 The cumulated relative reduction of the second child-generation of a minority that originally was one fourth of the total population, owing to mixed marriages. Different values of the parameters h and k.

k h

0,1 0.2 0,3 0.4 0.5 0,6

0.0 0.046 0.092 0.120 0.153 0.174 0.192 0.1 0.045 0.091 0.129 0.159 0.193 0.220 0.2 0.044 0.090 0.129 0.169 0.207 0.242 0.3 0.043 0.088 0.129 0.180 0.221 0.269 0.4 0.041 0.088 0.135 0.184 0.232 0.284 0.5 0.037 0.087 0.137 0.189 0.251 0.301

the decreasing proportion of the total population, results in an ever increasing loss for the Swedish minority. From the fourth to the fifth generation the loss is 22.1 per cent, and cumulated over all five generations it is 55.7 per cent. This means that the Swedish proportion of the fifth generation is only 11.1 per cent.

Besides the quantitative effects illustrated above, mixed marriages have a considerable qualitative impact on the minority and its composi- tion. This is clearly illustrated by the increasing proportion of the minority that has a heterogeneous background. In the example above, no less than 42.8 per cent of the Swedish children in the fifth genera- tion are descended from mixed marriages.

To illustrate the impacts of h and k, the total effect cumulated over two generations is presented in table 3. The figures in the table express the relative reduction of a minority that originally constituted one fourth of the total population.

Since the parameter h has a direct impact on the total effect through the function p, it is quite natural that it is an important factor in the long run. The influence of the parameter k is not equally predictable. On the one hand, an increasing value of k has a decreasing effect on the function p, but, on the other hand, a higher value of k results in a greater direct effect owing to language shifts. Therefore, the latter aspect is more pronounced for high values of h, when the influence of the linguistic conditions of the environment is greater.

Like most statistical models, the one used here is a rough simplifica- tion of reality. In this case this is so especially for the classification into 'endogamous' and 'exogamous' groups. In practice one should use a

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much more refined scale than that used here, which consists of the extremes only. As a consequence it is in general hardly meaningful to try to estimate the parameter h, or the function ux. This also means that the model should be used for illustrative purposes only. The essential point in this particular case is that the model clearly illustrates how, in a simplified situation, mixed marriages have a pronounced cumulative quantitative effect. Furthermore, that mixed marriages have a considerable qualitative impact on the minority is also illustrated by the model, and this is certainly of great importance for an understand- ing of the assimilation process.

References

Blau, Peter M., 1977, Inequality and heterogenity (Free Press, New York). Finn~is, Fjalar, 1982, Sprb&gruppsidentifikation och kunskaper i finska i Svenskfinland [Language

group identification and knowledge of Finnish in the Swedish settlement area], Ethnicity and Mobility Research report, no. 11.

Finn~ts, Fjalar, 1986, Den finlandssvenska befolkningsutvecklingen 1950-1980: En analys av en spr~tkgmpps demografiska utveckling och effekten av bland~iktenskap [The demographic development of the Swedish population in Finland 1950-1980: A study of the demography of a language group and the effect of mixed marriages] Svenska litteraturs~tllskapet i Finland, no. 533.

Mittelbach, Frank G. and Joan W. Moore, 1968, Ethnic endogamy - The case of Mexican Americans, American Journal of Sociology 74, 50-62.

Rust, Ph.F. and P. Seed, 1985, Equality and endogamy: Statistical approaches, Social Science Research 14, 57-79.

Thomas, John L., 1951, The factor of religion in the selection of marriage mates, American Sociological Review 16, 487-491.


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