Coital frequency among married and cohabiting couples in the United States. A comment.

PIP: This commentary refers to Rao and DeMaris' (1995) study of coital frequency among married and cohabiting couples in the US. The findings indicate higher rates of coitus among cohabiting partners. The sample includes couples with relationship durations of under 5 years. The authors of this critique argue that coital rates are more closely associated in nonlinear ways to duration of the relationship than to age of either partner. One 1983 US study indicates that mean coital rates decline by 50% during the first year of marriage, while another (1953) study indicates that rates decline by 50% from age 20 to 40 years. These two findings are compatible with the understanding that coital rates vary widely across couples and that couples marry at varying ages. The authors argue that cohabiting relationships are of shorter mean duration than marriages, and that this explains the higher coital rates among cohabiting couples. Coital frequency research could test the relationship between duration and coital frequency by matching coarse age (5-year intervals) and 1-2 month duration relationships of cohabiting couples with control married couples. It is possible that data are flawed if married couples believe the duration begins at the start of the legal marriage rather than the consensual union leading to marriage.^ieng