Family planning program managers may be easily misled by conclusions about the effects of price increases on the demand for services when the findings are based on pre-experiments such as the single-group pretest-posttest study, generally believed to be practical. This report presents financial and service data from clinics in Ecuador, which, analyzed according to the single-group pretest-posttest design, would suggest that the demand for intrauterine device services is inelastic. However, considerable demand elasticity is detected when data are analyzed according to more rigorous quasi-experimental designs. -from Authors