This book provides an in-depth analysis of an incumbent worker training program funded through California's unemployment insurance taxes. The Employment Training Panel (ETP) Program, the largest such program in the nation, is somewhat novel in that it is a preventive training program that offers additional skills to the employed in the hope of preventing firms from abandoning the state's economy or laying off workers. The authors combine a brief history of the ETP program, case studies, and quantitative analysis to evaluate the impacts of the program. In addition, they discuss and demonstrate effective evaluation methods, showing how the method they use can offer insights into the workings and impact of a variety of complex public programs and how it can generate clear public policy recommendations. The authors also provide guidance for policymakers and researchers interested in the methodological pitfalls associated with such evaluations.