Over the past 25 years sentencing guidelines have represented an important and substantial change in the US criminal justice system. Guidelines were passed to reform (or change) sentencing structures. To date, 19 states and the federal government have adopted some form of sentencing guidelines. Under guidelines, an offender's sentence is largely determined by his or her prior record and offense severity. Guidelines have shifted the structure of sentencing from an indeterminate model—where judges rely on an offender-centered approach that allows for relatively loose punishment ranges with prescribed maximums—to a determinate model. Sentencing guidelines, as a new model of punishment, move the system to a crime-centered approach with a structure that mandates more narrowly tailored punishments. The end result provides a substantial reduction in the discretionary power of judges to impose disparate sentences, along with an increased certainty with regard to the type of sentence that may be given.