The national divorce rate has been decreasing steadily since the 1980s. But not for couples over age 50. According to a study conducted by Bowling Green State University, the rate of so-called gray divorces has increased by more than 100 percent over the last 20 years, and there's no sign of it slowing down.In the study, sociologists predict that gray divorces will increase to 800,000 per year in 2030, up from 600,000 in 2009. In 1990, only one in 10 couples over age 50 divorced. That number increased to one in four in 2009. The chance of divorce is even greater for those couples who are on second or third marriages.