Same-sex partnership, same-sex marriage and family formation

It has long been argued that the legalization of same-sex marriage would have a negative impact on marriage. In this paper, I use data on OECD member countries for the period 1980-2010 to examine the effects of same-sex partnership and marriage laws on three indicators of family formation: marriage, divorce and extramarital births. The results from difference-in-difference models, which are robust to several specification checks, indicate that neither the introduction of same-sex partnerships nor the legalization of same-sex marriage had negative effects on family formation. These results are also confirmed when the synthetic control method is used to construct counterfactua indicators for each country that adopted a same-sex partnership or same-sex marriage law, although the results for extramarital births are somewhat less reliable.