A supply of crime equation has been theoretically developed which states that participation in illegitimate activity is a function of the certainty of punishment, the severity of punishment, legal income opportunities, and tastes. One of the first empirical attempts to test this theory was by Ehrlich, who expanded Becker's theory and tested the model using regression analysis with cross-sectional State data. In a more recent study, Forst claims to replicate Ehrlich's model using 1970 data. Forst states that his results show that Ehrlich's model tested with 1970 data show opposite results to those claimed by Ehrlich; Forst finds the deterrence variables to be weak and nonsignificant. In this article, the plan for replication of Forst's data was to compare Forst's model and results to Ehrlich's, to replicate Forst's results without the few errors found in his data, to consider Forst's functional form, and to consider Forst's choice of additional variables. Both Forst and Ehrlich developed their statistical models from the same basic theory. This analysis reveals that using 1970 data with additional exogenous variables alters the strong conclusions that Ehrlich found for 1960 but does not contradict what Ehrlich found. While Forst's research does point out that other than deterrence variables may have some impact on the crime rate, it does not imply that the deterrence effects of punishment are not significant or unimportant. Important questions still to be considered are what kinds of punishments deter what kinds of crimes and what is the relative crime reduction effect of punishment compared to other control variables. Two tables, equations, 10 footnotes, and 8 references are included.