The matter of same-sex marriage is perhaps the most significant policy issue in family law since the introduction of no-fault divorce in the late 1960s and 1970s. Much of the debate is focused on the question of equality, although issues of relationship stability, consequences for opposite sex marriages, and marriage culture are often brought up. One aspect that is seldom argued is the effect a same-sex union might have on the children within that union. The absence of any discussion on children no doubt reflects the unanimous consensus in the child development literature on this question—it makes no difference.

1 Despite the various differences in each study, all but a couple have the same conclusion: children of same-sex parents perform at least as well as children from heterosexual families. This conclusion, that there is no difference in child outcomes based on family structure, has played a major role in legal cases, legislation, popular culture, and professional opinions on gay family rights—including rights to adoption and marriage.2 As Justice Walker claimed, to suggest otherwise is to risk not being taken seriously. Study Random sample Gay sample size Contenta Comparison group size Time series data Gay or lesbian study Bailey et al. (1995) No 55 Hard None No G Flaks et al. (1995) No 30 Soft 30 No L Patterson (1995) No 26 Soft None No L Tasker et al. (1995) No 25 Soft 21 No L Golombok et al. (1996) No 25 Hard 21 No L Sarantakos (1996) No 58 Soft 116 Yes G & L Brewaeys et al. (1997) No 30 Soft 68 No L Golombok et al. (1997) No 30 Soft 83 Yes L Chan et al. (1998a) No 30 Soft 16 No L Chan et al. (1998b) No 55 Soft 25 No L McNeill and Rienzi (1998) No 24 Soft 35 No L Patterson et al. (1998) No 37 Soft None No L Gershon et al. (1999) No 76 Soft None No L Gartrell et al. (1999) No 84 Soft None Yes L Dundas et al. (2000) No 27 Soft None No L Gartrell et al. (2000) No 84 Soft None Yes L Barrett et al. (2001) No 101 Soft None No G Chrisp (2001) No 8 Soft None No L Patterson (2001) No 37 Soft None No L Fulcher et al. 2002) No 55 Soft 25 No L Vanfraussen et al. (2002) No 24 Soft 24 No L Golombok et al. (2003) No 39 Soft 134 No L Bos et al. (2004) No 100 Soft None No L Patterson et al. (2004) No 33 Hard 33 No L Stacey (2004) No 50 Soft None No G MacCallum and Golombok (2004) No 25 Soft 76 No L Wainright et al. (2004) Yes 44 Hard 44 No L Gartrell et al. (2005) No 84 Soft None Yes L Leung et al. (2005) No 47 Soft 111 No G & L Scheib et al. (2005) No 12 Soft 17 No L Stacey (2005) No 50 Soft None No G Wainright et al. (2006) Yes 44 Hard 44 No L Wright et al. (2006) No 156 Soft None No G Bos et al. (2007) No 99 Soft 100 No L Goldberg (2007) No 46 Soft None No G & L Balsam et al. (2008) No 281 Soft 55 No G & L Bos et al. (2008) No 63 Soft None No L Bos et al. (2008) No 152 Soft None No L Fairlough (2008) No 67 Soft None No G & L Fulcher et al. (2008) No 33 Soft 33 No L Goldberg et al. (2008) No 30 Soft None No L Oswald et al. (2008) No 190 Hard None No G & L Rothblum et al. (2008) Pop. 475 Hard None No G, L & T Rivers et al. (2008) Yes 18 Soft 18 No L Sutfin et al. (2008) No 29 Soft 28 No L Wainright and Patterson (2008) Yes 44 Soft 44 No L Bos (2010) No 36 Soft 36 No G Gartrell and Bos (2010) No 84 Hard 93 Yes L Lehmiller (2010) No 68 Soft 86 No G Power et al. (2010) No 455 Hard None No G & L Rosenfeld (2010) Yes 3,502 Hard >700,000 No G & L Regnerus (2012) Yes 248 Hard 2,988 No G & L Allen et al. (2013) Yes 8,632 Hard 1,189,833 No G & L Within the last 15 years there have been over fifty empirical studies considering the effects on children of growing up within a same-sex household.Despite the various differences in each study, all but a couple have the same conclusion: children of same-sex parents perform at least as well as children from heterosexual families. This conclusion, that there is no difference in child outcomes based on family structure, has played a major role in legal cases, legislation, popular culture, and professional opinions on gay family rights—including rights to adoption and marriage.As Justice Walker claimed, to suggest otherwise is to risk not being taken seriously.

Unfortunately, the literature on child development in same-sex households is lacking on several grounds.3 First, the research is characterized by levels of advocacy, policy endorsement, and awareness of political consequences, that is disproportionate with the strength and substance of the preliminary empirical findings. Second, the literature generally utilizes measures of child and family performance that are not easily verifiable by third party replication, which vary from one study to another in ways that make comparisons difficult, and which differ substantially from measures standardly used in other family studies.4 But most important, almost all of the literature on same-sex parenting (which almost always means lesbian parenting) is based on some combination of weak empirical designs, small biased convenience samples, “snowballing,” and low powered tests.5

This paper addresses these shortcomings by using the 2006 Canada census to study high school graduation probabilities of children who lived with both gay and lesbian parents in 2006, and to compare them with four other family types: married, common law, single mothers, and single fathers. Currently, the 2006 Canada census has several strengths compared to any other data set. First, it uses information from a country where same-sex couples have enjoyed all taxation and government benefits since 1997, and legal same-sex marriage since 2005.6 As Biblarz and Savci note, such legalization reduces the stress and stigma of homosexuality, and encourages honest participation in census questions.7 Second, not only does the census provide a large random sample, but married and common law same-sex couples and their children are self identified. 8 This is an important advantage over the US census. Third, because the child and parent records are linked together, the marital status and educational levels of the parents can be controlled for when analyzing child performance. Finally, because of the relatively large sample size, there is enough power to not only separate gay from lesbian households, but also enough to examine the gender mix of same-sex households.9

The point estimates for high school graduation show that there is a significant reduction in the odds of children living in same-sex homes completing high school. In the case of gay parents, children are estimated to be 69 % as likely to graduate compared to children from opposite sex married homes.10 For lesbian households the children are 60 % as likely to graduate from high school. A breakdown of performance by the sex of the child shows a more dramatic result. Daughters of gay parents are only 15 % as likely to graduate, while daughters of lesbian parents are 45 % as likely to graduate. Both sets of results are estimated with precision. On the other hand, sons of lesbian parents are 76 % as likely to graduate, while sons of gay parents are 61 % more likely to graduate. However, neither of these results are statistically significant. In general, the results for gays and lesbians respond differently to different controls, and differ from the results for the other family types. This, and the different graduation rates for sons and daughters, suggest that the two types of same-sex couples are much different and should not be categorized together in empirical work.

These results survive several robustness checks. Graduation rates may be different because school attendance rates are different, yet no statistical difference in the probability of attending school across the different family types is found. In fact, the point estimates indicate children of opposite-sex married parents are less likely to attend school. Various changes in sample restrictions and controls also leave the results unchanged.