The truly minimum rate is really low, though, at least for some societies. For example, if the U.S. imprisoned at the same rates as Norway (0.07%), it would have around 250,000 total prisoners. And even there the number is arguably higher than the absolutely necessary minimum. If you dig into who's imprisoned in Norway and why: 1) a full 20% of the prison population are there for administrative offenses like nonpayment of fines; and 2) most of the rest are there for nonviolent drug offenses.