Why your first marriage has a 50% chance of lasting

If you're about to walk down the aisle for the first time, beware there's a 50 percent chance the union won't last to your 20th anniversary, according to a new survey.

That number, however, hasn't budged much in the past three decades of data collected as part of the National Survey of Family Growth (NSFG).

The findings "show trends that are consistent with broad demographic changes in the American family that have occurred in the United States over the last several decades," the researchers write in the March 22 issue of the National Health Statistics Report. "One such trend is an increase in the time spent unmarried among women and men. For women, there was a continued decrease in the percentage currently married for the first time — and an increase in the percent currently cohabiting — in 2006–2010 compared with earlier years."