How a researcher defines the parameters of their study can drastically affect the results. In past studies, findings regarding same-sex relationship stability vary depending on how researchers decided what constitutes a relationship. For example, do you count only couples who are formalized, as in marriages or domestic partnerships? Or do you expand that definition to include partners who live together or couples who are only dating?
A problem with doing research on relationships involving same-sex couples and defining relationship in the first way—i.e., formalized relationships only—is that it ignores the fact that people in same-sex couples have more barriers and difficulties surrounding relationship formalization. Even though acceptance of non-heterosexual relationships has been steadily rising, it can still be difficult to tell friends and family about a partner of the same sex, let alone go to a courthouse to get a marriage license. Because of this, formalized relationships do not happen as often for people who are part of same-sex couples.
Add Health, on the other hand, asks each respondent to consider her most recent relationship—whatever that means to the participant herself. It also asks for details about that relationship, such as how long it has been going on, whether the couple lives together, and so on. For that reason, researchers at Bowling Green State University used Add Health data to shed light on aspects of same-sex relationships that had been difficult to pin down in previous studies.