It is natural to suppose that a prosecutor's conviction rate—the ratio of convictions to cases
prosecuted—is a sign of his competence. Prosecutors, however, choose which cases to
prosecute. If they prosecute only the strongest cases, they will have high conviction rates.
Any system that pays attention to conviction rates, as opposed to the number of convictions,
is liable to abuse. As a prosecutor's budget increases, he allocates it between prosecuting
more cases and putting more effort into existing cases. Either can be socially desirable …

It is natural to suppose that a prosecutor's conviction rate–the ratio of convictions to cases
prosecuted–is a sign of his competence. Prosecutors, however, choose which cases to
prosecute. If they prosecute only the strongest cases, they will have high conviction rates.
Any system which pays attention to conviction rates, as opposed to the number of
convictions, is liable to abuse. As a prosecutor's budget increases, he allocates it between
prosecuting more cases and putting more effort into existing cases. Either can be socially …