(CNN) - More and more baby boomers are untying the knot.
A new study from Bowling Green State University shows that divorce rates for people 50 and older more than doubled over the last 20 years.
In 1990, fewer than 1 in 10 people who were divorced were 50 or older. In 2009, that number was 1 in 4.
Researchers think the trend of living together before marriage in the 1970s and 1980s may partially be to blame.
Those surveyed in the study say longer life spans and changing ideas about what makes a good marriage also contributed to the change.
"When you are 60, 65, you retire," says Susan Brown of Bowling Green State University. "[You think], 'Well, I can live another 20, 25 years. Do I want to spend the rest of my life with that person? Is she or he making me happy?'"
The U.S. has one of the highest divorce rates in the world, with almost half of marriages ending in divorce.