There are 12 million visits to local jails. At any given day I can't remember the number exactly but it's about 800,000,. somewhere in that about 3.5 million people. 9 million individuals have some spent at least some time in jail. Prisons because by definition people are there longer there's less cycling. But estimates suggest that about 3% of inmates get released from prison over the course of a year.
Becky Pettit of the University of Washington and author of Invisible Men talks with EconTalk host Russ Roberts about the growth of the prison population in the United States in recent decades. Pettit describes the magnitude of the increase particularly among demographic groups. She then discusses the implications of this increase for interpreting social statistics. Because the prison population isn't included in the main government surveys used by social scientists, data drawn from those surveys can be misleading as to what is actually happening among demographic groups, particularly the African-American population.