This book, *Applied Mathematical Demography* by Nathan Keyfitz, is the second in a series of three books that provide an account of the mathematical development of demography. The first book, *Introduction to the Mathematics of Population*, covered the mathematical background, while this volume focuses on demography itself. The third book in the series, *Mathematics Through Problems*, supplements the first two with a sequence of problems and answers. The book addresses common questions in demography, such as the effect of a lowered death rate on the proportion of elderly people or the impact of abortions on the birth rate. It emphasizes the importance of adjusting intuition to align with mathematical findings and provides technical analysis to estimate the magnitude of effects. The content is designed to be useful for those working on population and related matters, whether they delve deeply into the mathematics behind the answers or not. Keyfitz notes that population theory has evolved rapidly and in various directions, making it impossible to include all applications in a single book. The book focuses on one-sex, one-species models with fixed age-specific birth and death rates, which are mathematically tractable but may not capture all real-world complexities. The author acknowledges the contributions of numerous students, colleagues, editors, and referees who helped refine the manuscript. The book is structured into several chapters, covering topics such as population growth, life tables, mortality comparisons, stable theory, birth rates, reproductive value, population characteristics, projection and forecasting, instability, kinship theory, microdemography, multi-state models, family demography, heterogeneity, and the epilogue on how we know the facts of demography. Each chapter delves into specific aspects of demography, providing both theoretical insights and practical applications.This book, *Applied Mathematical Demography* by Nathan Keyfitz, is the second in a series of three books that provide an account of the mathematical development of demography. The first book, *Introduction to the Mathematics of Population*, covered the mathematical background, while this volume focuses on demography itself. The third book in the series, *Mathematics Through Problems*, supplements the first two with a sequence of problems and answers. The book addresses common questions in demography, such as the effect of a lowered death rate on the proportion of elderly people or the impact of abortions on the birth rate. It emphasizes the importance of adjusting intuition to align with mathematical findings and provides technical analysis to estimate the magnitude of effects. The content is designed to be useful for those working on population and related matters, whether they delve deeply into the mathematics behind the answers or not. Keyfitz notes that population theory has evolved rapidly and in various directions, making it impossible to include all applications in a single book. The book focuses on one-sex, one-species models with fixed age-specific birth and death rates, which are mathematically tractable but may not capture all real-world complexities. The author acknowledges the contributions of numerous students, colleagues, editors, and referees who helped refine the manuscript. The book is structured into several chapters, covering topics such as population growth, life tables, mortality comparisons, stable theory, birth rates, reproductive value, population characteristics, projection and forecasting, instability, kinship theory, microdemography, multi-state models, family demography, heterogeneity, and the epilogue on how we know the facts of demography. Each chapter delves into specific aspects of demography, providing both theoretical insights and practical applications.