Marriage (Same Sex Couples)

Memorandum submitted by Mircea Trandafir, PhD (MB 136)

1. About the author:

2. Mircea Trandafir is an Assistant Professor (equivalent to lecturer in the UK system) in the Department of Economics at Université de Sherbrooke in Sherbrooke, Québec, Canada. He received his B.A. in Finance from the Academy of Economic Studies (Bucharest, Romania) in 2000, his M.A. in Economics from Central European University (Budapest, Hungary) in 2002, and his Ph.D. in Economics from the University of Maryland, College Park (Maryland, USA) in 2009. Starting in August 2013, he will join the Department of Business and Economics at the University of Southern Denmark (Odense, Denmark) as an Assistant Professor.

3. Dr. Trandafir’s primary research interests are in applied microeconomics, particularly labor and health economics. One line of his research and expertise relates to family formation, and specifically to the potential effects of the legalization of same-sex marriage on the marriage, divorce and childbearing decisions made by different-sex couples. In a series of papers, he provides causal estimates of the effects of the introduction of same-sex marriage on (different-sex) family formation. The first of these papers was awarded the 2009 Award for Best Comparative Paper presented at the Annual Meetings of the Association for Public Policy and Management.

4. Summary:

5. Same-sex marriage has been a hotly-debated issue in the Western world for several decades. Until today, only a handful of countries legalized marriage for same-sex couples and a few others, the UK included, introduced a separate institution for same-sex couples, similar to marriage (registered partnership or civil union). One argument almost always present in the debate is that the legalization of same-sex marriage would have a negative impact on (different-sex) marriage. In this written testimony, I present the results of my research that aims to answer this question and provide causal estimates of the effects of the introduction of same-sex marriage on (different-sex) family formation.

6. My research relies on the use of advanced econometric techniques to examine the evolution of various indicators of family formation following the legalization of same-sex marriage in the Netherlands (2001), Belgium (2003), Canada (2003) and Spain (2005), while taking into account the long-term trends in marriage, population change, and any other factors that could have an effect on family formation. My results invariably indicate that overall there were no negative effects from the legalization of same-sex marriage on several measures of family formation. After the introduction of same-sex marriage, there was no significant decline in (different-sex) marriage, nor was there a significant increase in the divorce rate or in the fraction of children born outside marriage.

7. However, I do find evidence that legalizing same-sex marriage does not affect all individuals in the same way. In the Netherlands, the first country that legalized same-sex marriage, more conservative couples seem to have married more and more liberal couples less after same-sex marriage became legal, although it is unclear if the latter is due to the legalization of same-sex marriage or to the availability of "civil unions" to different-sex couples.

8. The testimony:

9. One of the most common arguments in the debate on the legalization of same-sex marriage is that opening up marriage to same-sex couples would affect the value of marriage and family formation in general. According to this argument, by reducing the value of marriage, same-sex marriage would encourage other forms of family formation such as cohabitation. As a result, there would be fewer marriages, more extramarital births and possibly more divorces. In the United States, several recent laws were at least partly justified based on this argument, with the most prominent being state constitution amendments such as Proposition 8 in California or the Defense of Marriage Acts, laws preventing federal or state governments from recognizing (same-sex) marriages.

10. However, the effect of same-sex marriage on marriage and family formation is theoretically ambiguous. On the one hand, legalizing same-sex marriage could accelerate what sociologists call the "deinstutionalization of marriage:" a generalized trend of increased social acceptance of non-traditional family forms such as cohabitation instead of marriage, even after childbirth. Legalizing same-sex marriage could reduce the stigma on these non-traditional family forms, creating an environment where (different-sex) couples could increasingly choose these alternatives over marriage. On the other hand, same-sex marriage could be seen as "institutionalizing" same-sex couples and could then lead to more different-sex marriages if it reignites the interest in marriage. Finally, the legalization of same-sex marriage could reduce the pressure on government and on employers to provide benefits to cohabiting couples, making cohabitation less attractive when compared to marriage.

11. Despite the interest in this topic in the political discourse and in the media, there is very little empirical evidence on the effect of granting marriage rights to same-sex couples on family formation and most of it comes from correlation studies. My research fills this gap by providing the first causal estimates of the impact of same-sex marriage on family formation.

12. In the paper "The effect of same-sex marriage laws on different-sex marriage: Evidence from the Netherlands," I use aggregate data as well as detailed individual-level data from municipal registries in the Netherlands (the first country to legalize same-sex marriage) to study the patterns in marriage behavior after the legalization of same-sex marriage. Using advanced econometric methods and data from the other OECD member countries, I construct a counterfactual for the Dutch marriage rate, i.e., what the marriage rate would have been in the Netherlands in the absence of the same-sex marriage law. I then examine whether there were significant deviations in the evolution of the Dutch marriage rate from this counterfactual. My analysis shows that the same-sex marriage law had no significant effects on either the overall or the different-sex marriage rate. Using detailed individual-level data, I next analyze the marriage decision of various demographic groups. Interestingly, I find that the effects of the law are heterogeneous, with presumably more liberal individuals marrying less after the enactment of the law, while potentially more conservative individuals married more after the law. [1] However, it is impossible to distinguish if more liberal individuals marry less due to the same-sex marriage law or due to the availability of a marriage-like contract (registered partnership) to different-sex couples. [2] This paper is the first to estimate the causal effect of a same-sex marriage law on different-sex marriage and it was awarded the 2009 Award for Best Comparative Paper presented at the Annual Meetings of the Association for Public Policy and Management.

13. In a second paper, "Same-sex partnership, same-sex marriage and family formation," I use aggregate data for the period 1980-2009 on 28 OECD member countries, 14 of which introduced same-sex registered partnership or civil unions and 4 same-sex marriage during this period. I extend my previous analysis by studying three indicators of family formation: the marriage rate (both overall and separately for different-sex couples where appropriate), the divorce rate, and the extramarital birth rate (the fraction of births to unmarried mothers among live births). I rely on several strategies that eliminate the spurious effect of other factors that can influence family formation: long-term trends in attitudes toward marriage, changing population structure (aging, racial and ethnic composition, educational composition etc.), macroeconomic conditions etc. My results suggest that same-sex marriage laws had no negative effects on family formation. Indeed, the estimated effects generally point to slightly more marriages, fewer divorces and lower rates of extramarital births. I confirm the validity of these results by subjecting them to several econometric checks.

14. In conclusion, my research shows that legalizing same-sex marriage did not have negative effects on different-sex family formation in other developed countries. Given that these countries are similar to the UK in terms of their population structure and attitudes toward marriage, these results pertain directly to the current policy debate in the UK regarding the legalization of same-sex marriage.

March 2013


[1] I classify individuals as “potentially conservative” and “potentially liberal” based on voting patterns in their region of residence or based on their ethnicity.

[2] The result that presumably more conservative individuals marry more after the same-sex marriage law is not subject to the same limitation.

Prepared 13th March 2013