Prisoners who behave behind bars and participate in treatment classes are increasingly winning extra time off their sentences.

States under pressure to erase budget deficits and ease prison overcrowding are increasing the amount of time inmates can deduct from their terms behind bars when they take classes including job training or substance abuse treatment.

This year Colorado has passed a law allowing low-risk inmates 12 days per month of earned time instead of 10; Mississippi has lifted a 180-day cap on earned time; and Oregon has raised the amount of time inmates can deduct from their sentences from 20 percent to 30 percent.

Critics question whether rehabilitative programs offered behind bars can produce lasting improvements. But supporters say the law changes cut costs and motivate inmates to acquire life skills.