Ever since Bill and Melinda Gates announced that their 27-year marriage was over, one question has been on the lips of many talk show hosts and everyday folks: How can this be, after all that time together?

The billionaire philanthropists aren't the first high-profile couple to split up decades after tying the knot. Former Vice President Al Gore and his wife, Tipper, ended their marriage after 40 years. Though not divorced, actors Danny DeVito and Rhea Perlman separated after 30 years together.

According to the AARP, midlife breakups are much more common than a generation ago.

"Older adults today are much less likely to be willing to remain in what we call ‘empty shell marriages,’ “ says Susan L. Brown, codirector of the National Center for Family and Marriage Research at Bowling Green State University in Ohio.

In fact, the divorce rate for people older than 50 doubled between 1990 and 2010, though it has remained stable since then, according to Brown's research. As of 2019, that's 10 divorced people per 1,000 married folks 50 and older.

"Marriage now is more about self-fulfillment and personal happiness than it was decades ago,” Brown observes, “and we have very high expectations as to what constitutes marital success."

So what are some of the main culprits that lead to divorce after a long union?

• Infedelity

• Money Issues

• Lack of Communication

• Empty Nest

• Unresolved Issues of the Past