Nate Silver at FiveThirtyEight has an interesting little post up today suggesting that states with constitutional amendments banning same-sex marriage are more likely to have higher divorce rates. Silver uses statistics from the CDC to show that from 2003 until 2008, states with no constitutional ban on same-sex marriage experienced an average 8 percent decrease in divorce rates. Meanwhile, states that have enacted constitutional amendments banning same-sex marriage saw an average 1 percent increase in divorce rates over that time. Massachusetts, the first state to legalize same-sex marriage, has the lowest divorce rate in the nation, followed by Rhode Island, New Mexico and Maine — three states that don’t have constitutional amendments banning same-sex marriage. The seven states with the largest increase in the divorce rate during the five-year period all have constitutional amendments banning same-sex marriage. Texas is somewhat of an exception to the rule. Despite a 2005 constitutional amendment banning same-sex marriage, Texas saw a 3.6 percent drop in its divorce rate from 2003 to 2008. Silver concludes as follows:
The differences are highly statistically significant. Nevertheless, they do not necessarily imply causation. The decision to ban same-sex marriage does not occur randomly throughout the states, but instead is strongly correlated with other factors, such as religiosity and political ideology, which we have made no attempt to account for. Nor do we know in which way the causal arrow might point. It could be that voters who have more marital problems of their own are more inclined to deny the right of marriage to same-sex couples.
There is, however, probably now enough data on this subject to engage in more sophisticated longitudinal studies on this subject (more sophisticated than I have engaged in here), which might produce more robust conclusions. Although only Massachusetts has affirmed gay marriage for any length of time, the difference between the states which have banned it constitutionally versus statutorily may be worth examining, as the former represents a significantly more confident assertion about the nature of state-sanctioned marriage. At the very least, I would be surprised if there were any statistical evidence that interpreting the right of marriage to apply to same-sex couples would be injurious to heterosexual couples in any material way.