Policy evaluation research. Measuring the independent variables.

The purpose of this article is to evaluate the accuracy of three methods used to obtain policy data: (a) government agency surveys, (b) secondary sources, and (c) historical legal research. Changes in laws were identified for all 48 contiguous states for the period 1968 to 1994. Legal research is most accurate for well-established laws that have consistent legal descriptions across nearly all states. Laws that are recently enacted, adopted by only a few states, and treated in a legally inconsistent manner across states require a multistage data collection method to identify accurate policy change information.