Between 1991 and 2006, the numbers of unfaithful wives under 30 increased by 20% and husbands by a whopping 45%. These numbers come from a study conducted by David Atkins of the University of Washington Center for the Study of Health and Risk Behaviors. ... Since 1950, the age of first marriage has risen to 25 from 20 for women and to 27 from 22 for men. "It's more common for people to be hooking up or having relationships with multiple partners" before marriage, says Prof. Laumann. Even young people who engage in monogamous relationships before marriage may be hurting...