MIAMI (CBSMiami) – While some violent crime may be ticking down nationwide, the length of prison stays continues to grow, especially in the Sunshine State.

The Pew Center on the States released a new survey that found in 2009, prisoners served an additional nine months in custody, or 36 percent longer, than prisoners in 1990.

That extra time served is coming at a big cost to the states. Pew found that a total of more than $10 billion nationwide is being used to house prisoners the extra time. It breaks down to $23,300 per offender in 2009.

According to the Pew survey, Florida prisoners served an average of 3 years in prison in 2009. The prison stay was 166 percent more than the average prisoner served in 1990.

The biggest change came for sentences related to drug offenses which increased 194 percent from 1990 to 2009. Property crime sentences increased 181 percent and violent crime sentences increased 137 percent, according to the Pew survey.

Pew found that the average cost of one month in prison in Florida cost $1,713. Multiplying the per month cost times the additional time prisoners served of 22 months came out to $38,477 as an average cost to keep prisoners in jail longer.

For comparison purposes, the state of Florida spends around $7,000 per student in the public schools, or roughly 1/5 of the amount spent on prisoners.

Pew then multiplied the average cost times the number of prisoners released in 2009, 36,678, and came up with an additional cost of $1.4 billion the state of Florida spent to keep prisoners in jail longer.

The study’s director, Adam Gelb, said that the increase in sentences for non-violent crimes, specifically drugs, wasn’t helping keep the streets any safer.

“Taxpayers, today more than ever, want their dollars to produce the best possible public safety results,” said Gelb. “The idea behind longer prison terms is that they will cut crime and recidivism. But for a large number of lower-risk offenders, that just isn’t the case. There’s a high cost and little to no crime control benefit.”

A companion analysis Pew conducted in partnership with external researchers found that many non-violent offenders in Florida, Maryland and Michigan could have served significantly shorter prison terms with little or no public safety consequences.