California has experienced the greatest decline in incarceration of drug-related offenders of any major prison system since the state's Proposition 36 went into effect five years ago, according to a report from the Justice Policy Institute (JPI).

About 5,400 fewer drug offenders are now in the California prison system because of the voter-approved initiative, which calls for treatment rather than incarceration for low-level offenders. The report, "Proposition 36: Five Years Later," said that California had the biggest numerical decline in drug prisoners among the 10 largest states, although New York had a bigger statistical decline.

At the same time, California's violent-crime rate has been falling faster than the national average.

Spending on treatment has doubled since 2000, and the state has experienced the largest increase in treatment clients in the country.

JPI Executive Director Jason Ziedenberg said California had saved hundreds of millions of dollars because of Proposition 36. "In a state that has struggled with corrections and sentencing reform, Proposition 36 stands out as a successful way to reduce drug imprisonment," he said.