The director of a local reading camp made a similar point that stuck with me about the relationship between future prison populations and literacy rates. Don't know that any of this is official enough though.

Evidence shows that children who do not read by third grade often fail to catch up and are more likely to drop out of school, take drugs, or go to prison. So many nonreaders wind up in jail that Arizona officials have found they can use the rate of illiteracy to help calculate future prison needs.