These notes concern the historical statistics for modern local authorities, which have been created for Vision of Britain by re-districting statistics originally reported for other units. We have also had to deal with variations in the categories and classifications used in statistical reporting over the years.

• 1911: The data for England and Wales combine data from Table 2, "Tenements in the occupation of private families--Classified by Numbers of Rooms and by Numbers of Occupants, in each Administrative County and in the Aggregates of Urban Districts (Exclusive of County Boroughs) and of Rural Districts; also in Urban Districts (other than County Boroughs) and in Rural Districts, 1911", and Table 3, "Tenements in the Occupation of Private Families.--Classified by Numbers of Rooms and by Numbers of Occupants, Distinguishing Children under 10 Years of Age, in London and in each Metropolitan Borough, in each County Borough, and in each other urban district of which the Population Exceeded 50,000 Persons at the Census of 1911", in Tenements, England and Wales, Vol. VIII of the 1911 census reports. These tables cross-tabulate numbers of persons and numbers of rooms, unlike the later censuses which provide counts of numbers of persons living in specific density categories, so the latter type of measure has been computed on the assumption that households with 15 persons "or more" have precisely 15 persons, and that households with 10 rooms or more have precisely 10 rooms. However, over 99% of the population covered (all but 303,553 out of 34,590,606) lived in households with less than 10 rooms and 15 persons. The data for Scotland are calculated from Table 27, "Housing Conditions", in the 1911 County Reports, which includes categories for dwellings with 10-14, 15-19 and 20-24 "windowed rooms"; and for households with 15-19 persons. Each of these was assumed to have the number of rooms or of persons in the middle of the stated range, while the categories for households with zero rooms, presumably because the only rooms had no windows, were assumed to have 0.1 room. Any residuals falling outside the listed categories were ignored. These Scottish data were for counties, four cities and 22 major burghs, so they were first allocated to parishes in proportion to total population in 1911, then re-allocated to modern local authorities using a parish-level GIS.
• 1931: Data on persons per room were taken from Table 11, "Private Families, classified by size of family, rooms occupied, and density of occupation", in the County Reports for England and Wales, National totals for England and Wales are from Table 6, "Private families, classified by size of family, rooms occupied, and density of occupation (England and Wales, urban and rural aggregates, regions and London A. C.)", in Housing report and tables, England and Wales, 1931, p.20. Data for Scotland from table 29, "Population by Number Enumerated per Room", in the County Reports of the 1931 Census of Scotland. National totals are taken from Table 61, "Houses: Density of Occupation in Counties and Burghs", in Populations, ages and conjugal conditions, birthplaces, Gaelic speaking and housing, Scotland, Vol. II.
• 1951: Data on persons per room were taken from table 12 in the County reports of the 1951 census of England and Wales, "Private Households by Density of Occupation (Persons per Room)" for "Administrative County, Municipal Boroughs, Urban and Rural Districts", and from table 21, "Houses: Population by Number Enumerated per Room", in the Scottish County Reports. National Totals for Scotland also from Table 21. National Totals for England and Wales are from Table 8A, "Private Households by Density of Occupation (Persons per Room)" (p.47), although this uses a single category for densities "Over 2", where the county reports break the data down into "over 3" and "3 and over 2". The national total number of households comes from table 7 (p.46). Data on "amenities" were taken from table 13, "Private Households according to possession of certain household arrangements" for "Administrative County, County Boroughs, and Urban Areas with 50,000 population or more", and table 14, "Private Households according to possession of certain household arrangements" for "Urban Areas with Population of less than 50,000 and Rural Districts", in the County Reports of the 1951 Census of England and Wales; and from table 26, "Household Arrangements", in the County Reports of the 1951 Census of Scotland. National Totals for England and Wales from Table 11, "Private households by availability of certain Household Arrangements" for "England and Wales, Regions of England, Wales, Aggregates summary, Conurbations, London A.C. and County Boroughs with 500,000 Population or more" p58 of the 1951 Census for England and Wales Housing Report. National totals for Scotland from Table 56 in vol. III of Scottish census reports, "Households: Density of Occupation in Counties, Cities, Large Burghs. Aggregates of Small Burghs and Landward Areas".
• 1961: Data on persons per room were taken from table 19, "Population in all Private Households by Density of Occupation (persons per room)", and data on amenities were from table 23, "Private Households by availability of certain Household arrangements", both in the 1961 County Reports for both England and Wales, and Scotland. Data on tenure came mainly from Table 17, "Private Households, Persons and Rooms by Tenure", again in the 1961 County Reports both for England and Wales and for Scotland, with data for towns over 50,000 population in England and Wales, and over 10,000 in Scotland, selectively extracted from Table 16.
• 1971: Data on persons per room were taken from table 24 "Persons in permanent buildings by density of occupation (persons per room)", in both the England and Wales and the Scottish County Reports. Data on "amenities" and tenure were taken from table 25, "Enumerated households by tenure and household amenities" for "Administrative County, local authority areas, conurbation centres and new towns" in the County Reports of the 1971 Census for England and Wales; and from table 25, "Enumerated households by tenure and household amenities" for either "County of city, city wards" or "County, local authority areas" in the County Reports of the 1971 Census for Scotland.
• 1981: All data are taken from Table 10, "Tenure and amenities", for private households, in the 1981 Small Area Statistics, and were reported for Frozen Wards. The data were downloaded from the CASWEB online system on 23rd December 2016.
• 1991: Data on persons per room were taken from Table S23, "Persons per room: Households with residents; residents in households [100%]", in the 1991 Small Area Statistics, as downloaded from the NOMIS online system. Data on "amenities" and tenure were taken from Table S20, "Tenure and amenities: Households with residents [100%]", in the 1991 Small Area Statistics, again from NOMIS.
• 2001: For England and Wales, data on nunbers of persons per room are taken from Table UV083: "Persons Per Room: All Household Residents" in the Census Area Statistics Univariate Tables, listing numbers of persons living in households at different densities, as downloaded from CASWEB on 25th February 2017. The original data are for CAS Wards in England and CAS Electoral Divisions in Wales. This table is not available for Scotland, so numbers have been estimated starting from the counts of households in Table UV058, "Persons Per Room: All Households", then estimating counts of persons in 2001 by assuming that they had the same relationship to the counts of households in 2001 as the two counts had for the same district in 1991; then adjusting the resulting estimates of density categories so they summed to the actual total number of persons in 2001 for the district, this being reported in Table KS019. Data on tenure came from Table KS018, "Tenure: All households", and amenities from Table KS019, "Rooms, amenities, central heating and lowest floor level: All households", both in the 2001 Key Statistics release.
• 2011: Data on persons per room were taken from table QS410EW and table QS410SC, "Persons per room - People" in the 2011 Quick Statistics release. Similarly, data on central heating were taken from the "Central Heating" table in the Quick Statistics, Table QS415EW for England and Wales, and Table QS415S for Scotland. Data on tenure comes Table KS402EW for England and Wales, and KS402SC for Scotland.