[1] It has remained popular for over eighty years, in large part because of the simplicity of the calculation.
[2] Usually two Pearl Indexes are published from studies of birth control methods:[3] Like all measures of birth control effectiveness, the Pearl Index is a calculation based on the observations of a given sample population.
The culture and demographics of the population being studied, and the instruction technique used to teach the method, have significant effects on its failure rate.
[6] The Pearl Index also provides no information on factors other than accidental pregnancy which may influence effectiveness calculations, such as: A common misperception is that the highest possible Pearl Index is 100 – i.e. 100% of women in the study conceive in the first year.
The superiority of life table methods or other estimators that do not assume a constant hazard rate seems clear.