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What can science tell you about your relationship? A lot, as it turns out. Relationship research is a burgeoning field, and we seem to learn something new all the time about what makes marriages last and what makes couples happy. Here are five qualities of happy couples that might surprise you:
1. They're in sync with alcohol consumption: Whether couples don't drink at all, or enjoy a glass or two of wine with dinner each night, the key, according to recent research, is that the happiest couples tend to have the same views on alcohol consumption.
2. Their birth order is well-matched: While the science of birth order and personality isn't really, well, exact, recent research does indicate that a first-born paired with a last-born leads to the very happiest relationships. (Sorry, middle children.)
3. They take out the trash equally: A 2004 UCLA study found that couples who not only shared household chores and duties but also were clear on who did what and when were happier than those couples who had an unfair division of labor in the home.
See more: 5 Signs Your Relationship Needs Some TLC
4. They have more sex: A 2012 study found that couples who upped their sexual activity from once a month to once a week increased their happiness levels on par with getting a $50,000 boost in their annual salaries.
5. They're not yawning: A recent University of Arizona study found that men who were well-rested said they were more satisfied with their relationships than men who tended to get poor sleep at night.