Back in 2003, a pair of researchers from Pennsylvania State University attempted to answer a seemingly unanswerable question: What makes some marriages fall apart? They analyzed reasons given by about 200 divorced adults and published their findings in the Journal of Family Issues. (You can read the PDF here, if you like.)
Of the top four reasons, two are rather sad and serious: infidelity and substance abuse. The other half of the top four, plus many more down the list, represent the more nebulous reasons a relationship dissolves: incompatibility, growing apart, loss of love. And in a small number of cases — 3 percent — people said they simply didn't know why their marriages didn't last. Granted, there's only so much we can extrapolate from the experiences of just a few hundred people, but it's interesting all the same.