Book excerpt: A new theoretical criterion of housing unaffordability from a resident’s point of view is proposed in this book, tested with social data for respondents and price data for single-detached(-like) homes in two historically affordable mid-sized cities at two points in time, 30 years apart. This new criterion is derived from the magnitude of the mismatch between where the resident can afford to live and where they, realistically, would prefer to live. Housing affordability is a global social and political issue, and this book complements recent books that review housing affordability from a practitioner’s point of view. The book is written to be understood by everybody, with each chapter’s introductory subsection summarizing the subsequent technical and scientific sections. This book will therefore be readable not only for practitioners, but also academics in social science disciplines such as real estate, geography, economics, sociology, urban planning, and urban studies. Best of all, residents may utilize this book’s analysis of housing unaffordability to make wiser decisions about their own homes.