Prisons will be reduced by about 20,000 inmates over the next two years now that Gov. Arnold Schwarzenegger has signed a bill under pressure from federal courts to reduce prison overcrowding.

The plan combines previous reform efforts performed administratively by the Department of Corrections and Rehabilitation, the implementation of recently passed legislation, construction of new housing as well as a significant expansion of out-of-state transfers.

The 20,000 figure is about half the amount of inmates that were requested to be released by a panel of three federal judges in August.

The Schwarzenegger administration was under pressure from the panel, which ordered the state to reduce its inmate population in order to provide a constitutional level of health care.

Department of Corrections and Rehabilitation officials said it believes the state can move closer to a reduction of 40,000 prisoners in the next several years if lawmakers enact a number of changes. They include raising the property crime threshold for imprisonment for grand theft and allowing more prisoners to be sent to prisons out of state.

The department estimates its current and sought-after reforms can reduce the inmate population by more than 47,000 by 2015. Without additional legislative changes, the department projects a smaller reduction of about 35,000.