The land tax duplicates -- which ostensibly provide a complete yearly inventory of all landowners and tenants in every county in the United Kingdom, parish by parish -- are considered the most important systematic documentation available on British landed society between the Domesday Book of 1086 and the New Domesday of 1873. Throughout the past century the duplicates have been central to many questions at the heart of the most heated academic and political concerns, but their reliability as historical documentation has not previously been questioned systematically. In A Measure of Wealth, Donald Ginter launches a sweeping attack -- with devastating conclusions -- on the previous uses of the land tax duplicates as the evidential base of many of the leading questions in modern British historiography: the decline of the small landowner, the impact of enclosure, and the study of wealth inequalities.