Jon Stewart had a guest discussion the US incarceration rate. Our vast prison industrial gulag is unrivaled in scale in the world. Even police states put fewer people in prison. This situation is relatively recent - US prison population has exploded by a factor of roughly eight since 1973. Stewart and his guest mentioned the superpredator and three strikes hysteria, but mainly focused pm the racial. Disproportionate imprisonment rates for blacks are a significant fact, but racism was not invented in the 1970s or 80s in the US.
One non-negligible factor has been the rise of the private prison. Despite housing a relatively small proportion of total inmates, their very existence creates a potent political lobby to keep incarceration rates high. The state institutions have some similar incentives.
Many inmates, including many serving life sentences, have been convicted of relatively minor crimes, including drug possession and petty theft. The cost of this vast prison state within a state is large, not even counting the trail of ruined lives it leaves - perhaps 100 billion dollars per year or more.
It's time for the US to move beyond this infantile hysteria and study the examples of countries who have shown how to do it better - producing lower crime rates, lower incarceration rates, and better societies.