CORONA, Calif.  Mary Thompson, an inmate at the California Institution for Women here, was convicted of two felonies for a robbery spree in which she threatened victims with a knife. Her third felony under California’s three-strikes law was the theft of three tracksuits to pay for her crack cocaine habit in 1982.

Like one out of five prisoners in California, and nearly 10 percent of all prisoners nationally in 2008, Ms. Thompson is serving a life sentence. She will be eligible for parole by 2020.

More prisoners today are serving life terms than ever before  140,610 out of 2.3 million inmates being held in jails and prisons across the country  under tough mandatory minimum-sentencing laws and the declining use of parole for eligible convicts, according to a report released Wednesday by the Sentencing Project, a group that calls for the elimination of life sentences without parole. The report tracks the increase in life sentences from 1984, when the number of inmates serving life terms was 34,000.

Two-thirds of prisoners serving life sentences are Latino or black, the report found. In New York State, for example, 16.3 percent of prisoners serving life terms are white.