From the paper:
We therefore introduce two hypotheses. The first hypothesis is the main-effects hypothesis, which argues that the more traditional the value orientation of a religious or national origin group, the lower the risk of divorce.The data is supportive of the strong heterogamy hypothesis, according to which an AB has a higher chance of a divorce than the highest of AA and BB:
Our second hypothesis concerns the effect of the spouses’ religion and national origin, and argues that when the religions or national origins of the two spouses are dissimilar, the risk of divorce is higher.We call this the heterogamy hypothesis. Assumingthat the main-effects hypothesis is valid, we need to decide what constitutes evidence for the heterogamy hypothesis. If the divorce risk of a mixed marriage (between, say, a member of group A and a member of group B) is higher than the divorce risk of AA marriages but lower than the divorce risk of BB marriages, we argue that adaptation is taking place. The behaviour of those couples is in between the two groups, and one can argue that this is simply the average of the two group effects and not a heterogamy effect (Jones 1996). To analyse real heterogamy effects, we employ both a strong and a weak form of the heterogamy hypothesis. According to the strong heterogamy hypothesis, AB marriages will have a divorce risk that is higher than the maximum divorce risk of AA and BB marriages. For example, we expect that a marriage between a Catholic and an unaffiliated person will have a divorce risk that is higher than the (already) high risk for unaffiliated couples. According to the weak heterogamy hypothesis, AB marriages will have a divorce risk that is higher than the average risk of AA and BB marriages. In our example, the risk of the mixed group will be higher than the average of the low risk for Catholics and the high risk for unaffiliated couples.
Are there effects of heterogamy on the risk of divorce? Table 8 shows that the answer is clear: most mixed combinations have a risk of divorce that is higher than the highest level of divorce in the two homogamous groups. The average ratio is 2.02, indicating that mixed marriages have a risk of divorce twice as high as that of the maximum level of divorce in the two corresponding groups. This effect is quite strong and clearly supports the strong heterogamy hypothesis.The paper has detailed tables on the various combinations of intermarriage between different Dutch religious denominations and national origins. What seems clear is that Constantinus' ideas about religious and ethnic homogamy as more conducive to harmonious cohabitation seem to be supported by the data.
We also find variations in the magnitude of the effects that are consistent with our hypothesis about value orientations. Combinations of Dutch and Turkish or Moroccan persons reveal a stronger heterogamy effect than combinations involving Dutch and Western European persons. The effects for combinations involving Southern Europeans are in between the combinations with Turks or Moroccans and the combinations with Western Europeans. When looking at combinations involving
minority men, the differences are quite strong. The ratio is 4.7 for combinations involving Turkish men, 2.4 for combinations involving Moroccan men, and 1.5 for combinations involving Western European men. Because European groups are more similar than Moroccan and Turkish groups to the Dutch in values and lifestyle, this finding is consistent with theoretical interpretations of the heterogamy effect
in terms of value similarity.
Population Studies, Vol. 59, No. 1, 2005, pp. 71-85
Intermarriage and the risk of divorce in the Netherlands: The effects of differences in religion and in nationality, 1974-94
Matthijs Kalmijn et al.
A textbook hypothesis about divorce is that heterogamous marriages are more likely to end in divorce than homogamous marriages. We analyse vital statistics on the population of the Netherlands, which provide a unique and powerful opportunity to test this hypothesis. All marriages formed between 1974 and 1984 (nearly 1 million marriages) are traced in the divorce records and multivariate logistic regression models are used to analyse the effects on divorce of heterogamy in religion and national origin. Our analyses confirm the hypothesis for marriages that cross the Protestant-Catholic or the Jewish-Gentile boundary. Heterogamy effects are weaker for marriages involving Protestants or unaffiliated persons. Marriages between Dutch and other nationalities have a higher risk of divorce, the more so the greater the cultural differences between the two groups. Overall, the evidence supports the view that, in the Netherlands, new group boundaries are more difficult to cross than old group boundaries.