<prompt> Contraception efficacy is measured byPearl index onlyPearl index and life table analysisLife table analysis and couple protection rateCouple protection rate and pearl index  <response>: Two methods that have been used to measure contraceptive efficacy are the Pearl index and life-table analysis.Pearl index is defined as the number of failures per 100 woman-years of exposure HWYFailure rate per HWY Total accidental pregnancies Total months of exposure x 1200The Pearl index is usually based on a specific exposure usually one year and, therefore fails to accurately compare methods at various durations of exposure.The life-table analysis calculates a failure rate for each month of use. A cumulative failure rate can then compare methods for any specific length of exposure.Park 23e pg: 510 