The happiest marriages are between best friends.
A 2014 National Bureau of Economic Research study found that marriage does indeed lead to increased well-being, mainly thanks to friendship.
Controlling for premarital happiness, the study concluded that marriage leads to increased well-being — and it does so much more for those who have a close friendship with their spouses. Friendship, the paper found, is a key mechanism that could help explain the causal relationship between marriage and life satisfaction.
A study of 3,000 Americans who had ever been married found that age discrepancies correlate with friction in marriages.
The Atlantic's Megan Garber reports:
"A one-year discrepancy in a couple's ages, the study found, makes them 3 percent more likely to divorce (when compared to their same-aged counterparts); a 5-year difference, however, makes them 18 percent more likely to split up. And a 10-year difference makes them 39 percent more likely."