It has to do with alcohol.
The science:
Researchers analyzed how couples’ drinking habits changed after they moved in together and found that women’s habits have more sway than men’s do.
Expert insight:
When you first reach a new stage like cohabitation or marriage, you and your SO are both getting used to new expectations and ideals, says lead study author Geoffrey Leggat, research officer at La Trobe University's Centre for Alcohol Policy Research in Melbourne, Australia. In turn, you’ll have equal influence on each other’s habits in all areas.
While not always the case, women often take on the roles of caregiver and social coordinator over time, according to research and experts. (In same-sex couples, drinking habits will be more influenced by the person who is more involved in these elements of daily life.)
If that person is often—or rarely—scheduling nights out, chances are you’re drinking more—or less. Meanwhile, cutting back on booze is usually the result of caring behaviors like being concerned about one’s health.
The bottom line:
Separate research shows couples are less happy when one person regularly drinks more than the other. In an ideal world, if your SO cuts back, you would, too.