In twentieth century Britain, unemployment was the primary measure of economic distress. It has been measured in various ways: by the number receiving unemployment benefit, by sample surveys and, only at ten year intervals but perhaps most accurately, by the census.

The 1931 census came in the depths of the inter-war Great Depression, and several districts like South Tyneside -- containing Jarrow -- and Merthyr Tydvil in S.Wales had unemployment rates over 25%. The census was carried out in the spring, and rates in the depths of winter would have been significantly higher. Unemployment in Lancashire and Yorkshire was generally lower but still bad. The highest rate in the south-east was 16% for Tower Hamlets in the east end of London, but most places in the south-east had rates well below 10%.

After the 1939-45 war, new economic policies reduced the impact of the trade cycle, and the 1951 census generally revealed almost full employment: the highest rate was 8% for Merthyr Tydvil, and the most conspicuous feature of the map is the high rates around the coast, due to seasonal unemployment in seaside resorts.

Following the post-war boom of the 1950s and 1960s, unemployment rose over the 1970s and 1980s. In some areas, 1991 unemployment was higher than in the inter-war slump: Knowsley, on the edge of Liverpool, had 15% unemployment in 1931 but 31% in 1991.