Estimating contraceptive efficacy: the case of spermicides
The contraceptive efficacy of certain contraceptives, including vaginal spermicides, can be difficult to assess. This paper presents and evaluates available data on spermicides and discusses their implications. In addition, the authors call for further discussion of how to satisfactorily evaluate methods such as this that are only moderately effective in preventing pregnancy.
Contraception (Feb 2013) Vol. 87, Issue 2, Pages 134-137. (no abstract)