At one time, divorce among spouses over the age of 50 was considered so rare that, for all intents and purposes, it didn't happen. Of course, that was not exactly true, but it was the case that divorces between spouses aged 50 to 64 were much less common than they are now. Even as recently as 1990, divorces between spouses over the age of 50 made up only around ten percent of all divorces. Pittsburgh divorce attorneys have noted that by 2009, that same age group accounted for closer to 25 percent of all divorces.
One reason for the spike in divorce for over-50s is that baby boomers have been moving into this age group. Not only are baby boomers numerous, but as a group they prefer marriage to maintaining an ongoing relationship without getting married. Even when they have previously been divorced, baby boomers are very likely to remarry. This predilection for marriage means that there are more divorces among baby boomers than among other age groups that are statistically more likely to live with a partner without getting married.
What is interesting about the trend for baby boomers to be divorcing is that the overall divorce rate in the United States has been falling. Baby boomers have been bucking trends their whole lives, and they have not stopped yet.
Some observers have also pointed out that retirement can be a stressful time in a marriage. Spouses who have not been spending all of their time together often find that they have to rearrange their daily routines and get used to being around each other for more of the day. Spouses with marriages that are already in trouble often find this transition to be more than they can handle, leading to divorce.
Source: Orl. Sentinel "Aging baby boomers boost divorce rate among older adults" Dec. 14, 2011