Final answer:
Unplanned pregnancies are NOT a factor in the rising rates of cohabitation; however, later marriages, acceptance of cohabitation, and financial reasons do contribute to this trend.
Step-by-step explanation:
The factor that is NOT a contributing factor to the increased rates of cohabitation among U.S. couples is unplanned pregnancies. The factors that do contribute to this trend are getting married at later ages, increased acceptance of cohabitation, and financial and economic issues. As societal norms shift, there is less pressure to marry immediately, allowing individuals to prioritize education and careers. Couples are also using cohabitation as a way to spend more time together or to save money on living expenses, viewing it as a 'trial run' for marriage. In fact, there has been an increase in median age at first marriage, with data showing the age to be twenty-six for women and twenty-eight for men, the highest it has ever been according to U.S. Census records.