This book presents the culmination of our collaborative research, going back over 15 years (Rogers & Little, 1994), and for one of us, even longer (Rogers, 1967, 1973). It addresses a dif?cult, yet necessary, area of demographic research: what to do in data situations characterized by irregular, inadequate, or missing data. A common solution within the demographic community has been what is generally referred to as “indirect estimation�. In our work the focus has been on the indirect estimation of migration, and our use of the term “indirect� follows the description given in the 1983 United Nations manual, which de?ned it as “techniques suited for analysis of incomplete or defective demographic data� (United Nations, 1983, p. 1). We wrote this book with a goal to make it accessible to a reader familiar with introductory statistical modeling, at the level of regression and categorical data an- ysis using log – linear models. It is primarily intended to serve as a reference work for demographers, sociologists, geographers, economists, and regional planners.