James Q. Wilson, America's premier social scientist, notes that "the typical criminal commits from 12 to 16 crimes a year (not counting drug offenses)" and says that 10 years of scholarly studies "have shown that states that sent a higher fraction of convicts to prison had lower rates of crime, even after controlling for all of the other ways -- poverty, urbanization, and the proportion of young men in the population -- that the states differed. A high risk of punishment reduces crime. Deterrence works."
Is incarceration a deterrent to potential wrongdoers in society, or does it simply take proven malefactors out of society or both? Whichever...this is a worthwhile article. Pretty clearly the "three strikes" laws have done a world of good.