In one of the first large-scale comparisons of the children of same-sex parents to other types of parenting, children raised by gay and lesbian couples were only 65 percent as likely to graduate from high school as those raised in traditional two-parent households, even after controlling for factors such as income and education of the parents.
The study, "High school graduation rates among children of same-sex households," by Douglas W. Allen, professor of economics at Simon Fraser University, Burnaby, British Columbia, was published in the newest edition of the journal, Review of Economics of the Household.
Unlike previous studies of same-sex parenting, Allen was able to conduct a large-scale side-by-side comparison of same-sex parenting to other family structures - such as single parents and unmarried opposite sex parents - using the 2006 Canadian census.
In Canada, same-sex couples have been recognized since 1997 and Canada has recognized same-sex marriages since 2005. Also, the Canadian census asks whether one's parents were a same-sex couple and whether they were married or unmarried.
One of the most striking findings of the study was that the children of same-sex couples also had lower graduation rates than the children of single parents.
The study also found that daughters of same-sex parents had lower graduation rates than sons. And, daughters of gay couples, two men, have significantly worse graduation rates than the daughters of lesbians, two women. Among the sons of same-sex couples, the opposite is true - those with two dads are better off than those with two moms.
Previous social science studies have shown that the children of biological, intact, two-parent households perform significantly better on a wide range of measures, including graduation rates. But, same-sex parenting has proven difficult to study because reliable data requires large, random samples; and large, random samples typically do not have enough same-sex parents to draw conclusions about the population.
One other study that came close to Allen's accomplishment was the 2012 New Family Structure Study, conducted by Mark Regnerus, associate professor of sociology at the University of Texas at Austin. Due to limitations with the sample, though, the NFSS had to collapse a number of categories, such as cohabiting same-sex parents, single gay parents, and parents who were in a heterosexual relationship divorced and entered a same-sex relationship. Allen's study did not have that limitation.
In an article for The Witherspoon Institute's Public Discourse, Regnerus says that Allen's study has, like all studies, its own limitations. It does not, for instance, distinguish between same-sex married parents and same-sex common law marriage parents.
Regnerus believes, though, that those "limitations are modest in comparison to its remarkable and unique strengths - a rigorous and thorough analysis of a massive, nationally-representative dataset from a country whose government has long affirmed same-sex couples and parenting. It is as close to an ideal test as we've seen yet."
The American Psychological Association and American Sociological Association have claimed that there are no differences between same-sex parenting and parenting with both a mom and a dad. That conclusion, though, was based upon studies that use small, non-random samples. Regnerus believes that Allen's study should bring doubts to their conclusion.
"Might the American Psychological Association and American Sociological Association have been too confident and quick to declare 'no differences' in such a new arena of study, one marked by the consistent reliance upon small or nonrandom 'convenience' samples? Perhaps. Maybe a married mom and dad do matter, after all," he wrote.