Factors in long-term marriages

"The present study involves a nonrandom sample of 351 [U.S.] couples who have been married 15 years or more. Differences were found in the reported reasons for staying together between happy, unhappy, and mixed (one partner happy and one unhappy) marriages. For happy couples, the most frequently mentioned reasons for staying together was the perceived nature of the relationship, then the belief in marriage as a long-term commitment. Among the mixed and unhappy marriages, the most frequently named reason was the belief that marriage is a long-term commitment. Nineteen percent of those in mixed marriages and 47% in unhappy marriages said the children kept the marriage together."