Stability Across Cohorts in Divorce Risk Factors - Bishop Ireton High ...

342 Demography, Volume 39-Number 2, May 2002
The effect of the husband being older on divorce is positive in both the bivariate and
additive effect models. The effect of the wife being older is substantial. In the interaction
effect model, if a wife is five or more years older than her husband, the risk of divorce is
88% higher in comparison with a marriage that has relative age homogamy. The effect of
the wife having more education is also positive, although not significant using the BIC
criterion for strong evidence, increasing the risk of divorce by 9% at each marital duration.
The effect of the wife’s education is interesting in that it reverses direction between
the bivariate model and the two multivariate models. In the bivariate model, the risk of
marital disruption decreases 6% for each additional year of schooling the wife has. In the
multivariate models, the risk of divorce increases 4%–5% for each additional year of the
wife’s schooling. The switch from a negative to a positive effect is due mostly to the
inclusion of the control for husband’s education (results not shown). More-educated
women are generally married to more-educated men, and the effect of the husband’s education
is substantial and negative.
The effect of being Catholic is to reduce the risk of marital dissolution, and the effect
of the wife’s parents having divorced is positive. In both cases, though, the effect is reduced
somewhat with the introduction of the other covariates. In the interaction model, at
each marital duration, Catholics are 11% less likely to divorce, and couples in which the
wives’ parents divorced are 38% more likely to divorce.
There is no difference between whites and respondents reporting neither white nor
black race in the risk of marital dissolution. Blacks are substantially more likely to divorce
at each marital duration than are whites. However, this effect changes across time.
In the 1950–1954 cohort, the risk of divorce for blacks is 83% greater (1.97 × .93 = 1.83).
In the 1980–1984 cohort, the risk of marital dissolution for blacks is only 19% higher.
This pattern results from the fact that the risk of marital dissolution increases more slowly
(by a factor of .93) for blacks than for whites.
A Test for Proportionality
All the models estimated up to this point assume that the effects of the covariates are
proportional. That is, the effects of the predictor variables are assumed to be equal at all
marital durations. A test for proportionality is key for the purposes of this study to account
for the possibility that historical shifts in the risk of divorce may be confused with
nonproportionality. In particular, a variable with an effect that increases (decreases) with
marital duration may be mistaken for a variable with an increasing (decreasing) effect
across historical time.
In general, two rationales have been put forward to suspect nonproportionality. First,
as marriages mature, individuals accrue more marital-specific capital (Becker et al.
1977), decreasing the risk of divorce. Thus, individual couples change with respect to
their risk of marital disruption. Second, as marriages progress, a process of sorting occurs,
weeding out couples who are less suited to each other or less committed to a permanent
relationship (Morgan and Rindfuss 1985; South and Spitze 1986; Teachman
1986). The remaining marriages are therefore composed of couples who are less likely to
divorce.
The empirical evidence is limited, but a number of researchers, using different data
and methods, have found that the effect of age at marriage is stable across marital duration
(Morgan and Rindfuss 1985; South and Spitze 1986; Teachman 1986; Thornton and
Rodgers 1987). Morgan and Rindfuss (1985) reported that the positive effect on divorce
of having a premarital birth declines at longer marital durations, but Teachman (1986)
found a more consistent effect for this variable. South and Spitze (1986) and South (2001)
indicated that the effect of the wife’s education changes from being negative to being
positive as marriages mature. Again, however, Teachman (1986) found a consistent effect
of the wife’s education across different marital durations.