The massive expansion in Americans' prisons
contributed
little to the decrease in crime rates of the past two decades.
US imprisonment does tremendous human damage. Whether it harms the
economy depends on who you include in "the economy". It may be good
for the plutocrats in general. since some of them profit from prisons
or employ prisoners as slave labor, and the rest consider many
Americans superfluous. Prisons (which tend to kill prisoners who get
sick) may be their method of choice to dispose of the superfluous.