The concept swiftly spread to other states, but none of them chose to adopt a law as sweeping as California's. By 2004, twenty-six states and the federal government had laws that satisfy the general criteria for designation as "three-strikes" statutes—namely, that a third felony conviction brings a sentence of 20 to life where 20 years must be served before becoming parole eligible. A 1997 study found that in California, "the three-strikes law did not decrease serious crime or petty theft rates below the level expected on the basis of preexisting trends."