Contraception effectiveness percentages reflect typical per-year use rather than per-event use
the verdict
SUPPORTED
the evidence backs this
confidence 88/100
Contraception effectiveness and failure percentages are standardly reported as typical-use or perfect-use rates over a one-year period (such as per 100 woman-years) rather than as a probability per individual sexual act.
Evidence for · 3
Typical-use contraceptive failure rates in 43 countries with Demographic and Health Survey data: summary of a detailed report
2016 · cited by 105
The study estimates typical-use contraceptive failure rates across 12, 24, and 36 months of use, reflecting per-year risk rather than per-event risk.
See more details
More for · 2
Perfect-use and typical-use Pearl Index of a contraceptive mobile app
2017 · cited by 84
The study evaluates the typical-use Pearl Index as the number of pregnancies per 100 woman-years, tracking failure over annual periods of use.
Perfect- and typical-use effectiveness of the Dot fertility app over 13 cycles: results from a prospective contraceptive effectiveness trial
2019 · cited by 39
The study determines typical-use failure rates using multi-censoring life-table analysis over 13 cycles, which corresponds to per-year use effectiveness.