Tyler Cowen summarizes Justin Wolfers and Betsey Stevenson, whose research says that Matrimony Has Its Benefits, and Divorce Has a Lot to Do With That:
In the United States, the availability of divorce has increased with unilateral divorce, which allows either member of the couple to dissolve the union. The change has been associated with lower rates of female suicide and domestic violence, and fewer wives murdered by their husbands. Unilateral divorce shifts the bargaining power to the person who is getting less out of the marriage and thus is most likely to leave. The partner getting more from the marriage has to work harder to keep the other person around, which can be good for the marriage and good for the couple. In other words, unilateral divorce benefits victims and potential victims.When unilateral divorce was adopted, divorce rates rose sharply in the two years that followed, reflecting a pent-up demand for divorce. But after 10 years had passed, the divorce rate went back to normal or in some cases, compared with states without unilateral divorce, it had fallen further.
In fact, the divorce rate for married couples peaked in the United States in 1979, when it was 22.8 per thousand married couples per year. Since then it has continued to decline, reaching 16.7 divorces per thousand married couples in 2005.