Since the early 1970s, U.S. states have adopted a series of sentencing reforms that have substantially altered sentencing and release policies by limiting discretion of judges, parole boards, and/or prison administrators. The current study assesses shifts in year-to-year changes in new commitments and parolees returned to prison within all 50 states from the years 1972 to 2008. The study tests the theory that sentencing reforms resulted in increased commitments to prison due to changes in the structures of sentencing and not due to increased crime. Data was analyzed using panel regression with robust standard errors, fixed effects, and conditional change scores. By treating six main sentencing reforms as dynamically interacting, the results suggest that certain combinations of sentencing reforms significantly increase new commitments while the number of parolees returned to prison was not meaningfully affected. The analysis further indicates that the combinations that the reforms appear in at the state-level influence the magnitude of the impacts of reforms.