This machine-readable version of John Williams' <i>Digest of Welsh Historical Statistics</i> is the result of a collaboration between the Statistical Directorate of the National Assembly for Wales, the History Data Service and the Centre for Data Digitisation and Analysis at Queen's University Belfast. John Williams' <i>Digest of Welsh Historical Statistics</i> is intended to provide a service for those working on the history of modern Wales. It arises from a belief that the quantitative element is a necessary and important part of the historical record; from an awareness that it was an aspect that was particularly inaccessible for scholars of Welsh history; and from a conviction that some encouragement in the use of quantitative material was necessary. It is modelled on the two volumes dedicated to British historical statistics: Mitchell, B.R. and Deane, P. (1962) <i>Abstract of British historical statistics</i> and Mitchell, B.R. and Jones, H.G. (1971) <i>Second abstract of British historical statistics</i>. Number of houses, inhabited, uninhabited (and building, 1811-1921), by county, 1801-1971 (a) Number of private households, by county, 1801-1901; (b) number of private households, dwellings, rooms and density of occupation, by county, 1911-1971 Number of rooms occupied by private households, by county, 1911-1971 Brick production: (a) return of duties paid on bricks, by region, 1829-1849; (b) number of bricks and amount of duty paid, by county, 1836-1846 Number of house plans approved, by town, South Wales, 1851-1914 Estimated costs of building plans passed by Urban Districts, by type of building, 1909-1939 Total number of houses built in inter-war years, by county, 1919-1940 Number of houses authorised, under construction and completed, local authority and private enterprise, 1919-1939 and 1946-1974; by county 1919-1939; by county borough 1919-1939; number of houses demolished 1947-1974 Decisions on planning applications, by type of development, 1962-1972 Houses completed, by number of bedrooms, public and (from 1963) private sectors, houses and flats, 1945-1974 Government financial contributions, new houses and improvement grants, 1950-1974 Number of conversions and improvements, approved for grant, by public and private sector, 1955-1974 Prices and costs, 1958-1974 Please note: this study does not include information on named individuals and would therefore not be useful for personal family history research.