Sources and method

Every number on this site can be traced to a published source. This page lists them and describes how the derived measures are calculated.

The sources

Source	Used for	Licence
Nomis, 1961 Census (tables ST01, SH01, SH03)	County population, tenure, country of birth, households	Open Government Licence v3.0
Nomis, 2021 Census (TS001, TS054, TS012)	The modern half of each county comparison	Open Government Licence v3.0
ONS mid-year population estimates	County population for 1981 to 2021	Open Government Licence v3.0
ONS Open Geography Portal	County and country outlines, and land area	OGL v3.0, contains OS data © Crown copyright
Our World in Data	World and continent population, life expectancy, urbanisation, child mortality, emissions, nuclear warheads, objects launched into space, Red List Index	CC BY 4.0
World Bank	UK life expectancy, birth rate, urbanisation, infant mortality, homicide, internet use, land area	CC BY 4.0
Met Office HadUK-Grid	UK annual mean temperature	Open Government Licence
Natural Earth	Country outlines at world and continent level	Public domain

County population, 1961. Summed from the districts inside each county rather than read from the county row. Summing the districts also picks up the county boroughs, which were administered separately at the time. The two methods were checked against each other for Berkshire, Norfolk, Somerset, Northumberland and Warwickshire and agree exactly.
Households owning their home. Owner-occupied households divided by all households, worked out inside a single table so that the 1961 sampling basis cancels out of the ratio rather than biasing it.
Residents born outside the UK. For 1961, every category in the source table is a country outside the UK, so the total is their sum over the resident population. For 2021, it is all usual residents minus those born in the United Kingdom.
People per household. Persons in households divided by households, from the same table in each year.
Population change. Simple percentage change between the two selected years. Where a change exceeds 1,000% it is shown as a multiple, because a percentage stops carrying meaning at that scale.

The 1961 population table is a 10% sample scaled by ten, so it carries sampling error.
1961 figures are a census count; 1981 onward are mid-year estimates. They are different instruments and are labelled as such.
World and continent figures are estimates compiled from UN and historical sources, never counts, and carry an "estimate" badge on the page.
1961 has no sub-county breakdown here, because 1961 district boundaries are not available under an open licence. That year is shown at whole-county level.