In probably the most reliable survey ever done on divorce, by Joan Kelly, Ph.D. and Lynn Gigy, Ph.D from the Divorce Mediation project in Corte Madera, California, only 20% to 27% of couples said an extramarital affair was even partially to blame for their divorce.
In contrast, 73% to 80% of divorced men and women said their marriage broke up because they gradually grew apart and lost a sense of closeness, because they didn’t feel loved and appreciated.