The first census in 1801 simply divided people into those employed in agriculture and those in trade or manufacturing, and the 1841 census, the first to gather detailed occupational data, imposed no real order on it at all. However, the first occupational classification, introduced in 1851, was clearly concerned with social status as well as with what people made: it began with the Queen, followed by government officials and then by 'the learned professions'.

In the twentieth century a separate system of social classes was devised. Originally created to help understand mortality, the Registrar General's Social Classification was tabulated by the census from 1951 onwards. To provide a longer perspective we have re-organised earlier occupational information to the same system. Like the published 1951 data, all our figures are limited to men.

This is only possible where we have very detailed occupational statistics at district-level, so these earlier censuses are limited to 1841, where the replies to the occupational question were tabulated almost raw; 1881, where we can use complete data from the enumerator's books; and 1931, which produced the most detailed of all occupational reports. The 2001 data are based on a rather different system, so comparisons over time are tricky.