|Since 1980, the prison population has grown by a factor of 5|
|No matter how many prisons they build, they are always full|
The prison population has gone up irregardless of economic boom or bust. The cohort at the bottom of the ladder, where failure lives and breathes, has been growing. Implied in that is the group right above the prison populations, the part of society where people make bad decisions and screw up their lives, but don't manage to go to prison, has been growing apace. Something in society over the last 30 years has been breeding bad behavior.
The next time you read some economist droning on about income inequality think about these charts and what they might mean.