The authors apply modern theoretical and statistical methods to the unique data source of Domesday Book (1086) to analyse the system of manorial production and the nature of the national tax system known as danegeld in eleventh‐century England. Domesday Book includes detailed information on land ‘ownership’, income, resources, and fiscal responsibility for almost every manor in 1086 and, in some cases, in 1066. As no other document of any period or country can match either its detail or comprehensiveness, William the Conqueror's survey provides a rich database for modern economists. By using methods not previously applied to this period, the authors provide a new interpretation of the Anglo‐Norman economy—the first since the work of J. H. Round and F. W. Maitland a century earlier. This classic study has been responsible for stimulating the interest of, and further research by, quantitative economic historians in the medieval period.