Women’s decisions about whether or not to use contraception are more impactful than their decisions about which methods to use. This according to a study sample of 50,000 women of childbearing age which studied the effects on the nonmarital pregnancy rate of movements along 2 different margins of contraceptive behavior: the extensive margin, which captures decisions about whether to initiate use of any method of contraception among noncontraceptors; and the intensive margin, which captures the choice of methods among contraceptors. The study revealed:
• The impact on the number of nonmarital pregnancies would not be substantially different if noncontraceptors adopted long-acting methods than if they began using oral contraception.
• The nonmarital pregnancy rate would be reduced by about twice as much if a subset of noncontraceptors began using condoms as if an equal number of pill users took up long-acting methods.
Citation: Thomas A, Karpilow Q. The intensive and extensive margins of contraceptive use: Comparing the effects of method choice and method initiation. [Published online ahead of print March 29, 2016]. Contraception. doi:http://dx.doi.org/10.1016/j.contraception.2016.03.014.