Objective: Sentencing guidelines, statutory presumptive sentencing, determinate sentencing, truth in sentencing, and three strikes are important components of the criminal justice system. The main purpose behind a relatively-fixed sentence is to remove judicial discretion by insuring that convicted felons receive a reasonably-assumed sentence depending on the crime committed. The current study assessed shifts in year-to-year changes in incarceration rates within all 50 states from the years 1965 to 2008 due to the adoption of sentencing reforms.

Methods: The study tests two competing theories, a normative theory and critical theory of the expected effects of reforms on imprisonment. Data was analyzed using panel regression with unit-specific fixed effects, conditional change scores, panel corrected standard errors, and a new measure of reforms.

Results: This study, possibly due to differences in model specification, ran counter to a number of previous studies and suggests some "front-end" sentencing reforms and "back-end" release changes are, on average, related to changes in imprisonment.

Conclusions: The study concluded, that when significant, reforms increased more than decreased prison growth in comparison to indeterminate sentencing. Additionally, the analysis concludes that changes in release mechanisms and parole decision structures are driving increased growth more than changes in sentencing structures.