Although I hope the results reported here are useful to technically sophisticated political methodologists in building better models of ecological inference, my primary intended audience for this book is political scientists and others who need to make ecological inferences in real academic research, scholars for whom the substantive answer matters. Thus, the qualitative overview in Chapter 1 assumes no statistical knowledge. Parts I, II, and IV assume familiarity with linear regression. Although Parts III and V introduce a variety of tools to solve the ecological inference problem, most of the exposition assumes knowledge of only basic maximum likelihood methods (such as Cramer, 1986 or King, 1989a).