Industry in decennial census data refers generally to the primary business (i.e., the kinds of goods or services provided) of the person’s employer, or of the person in case of those who are self-employed. Thus, for example, a mining company (who employees would be classified in the mining industry, or a larger industry grouping including mining) might include employees with a variety of occupations, such miners, engineers, clerks, managers, etc.
The 1820 census included a tally by household of the number of persons (including slaves) “engaged” in three categories (agriculture, commerce and manufactures); and the 1840 census included a similar tally of persons “employed” in seven categories (mining; agriculture; commerce; manufactures and trades; navigation of the ocean, navigation of canals, lakes and rivers; and learned professions and engineers). While these categories were not comprehensive or precisely defined, the information collected represents the first data on industry (or industrial groups) in the decennial census. A question on industry was included in every census from 1910 to 2000, along with a question on occupation. The classification of industries became more systematic with more hierarchy during the 20th century. In the 2000 census, for example, the classification system included 265 detailed industry categories, which were collapsed to as few as 13 major industrial categories in data products from the 2000 census.
Figure 17-1 presents consistent estimates of major industrial groups for the United States from 1910 to 1990, as developed by Matthew Sobek (2006), tables on industry, in Historical Statistics of the United States: Millennial Edition, Vol. 2, pp. 2-101 to 2-107. These estimates are for 14 major industrial groups, reflect the 1950 census classification system, and are based on the Integrated Public Use Microdata Series (IPUMS). (See Minnesota Population Center, no date, “IPUMS-USA, Frequently Asked Questions (FAQ)”) Figure 17-1 presents also industrial group data as published in the 1990 and 2000 censuses. Figure 17-2 presents data published in census volumes for the United States by region for industrial groups for 1820 and 1840 (as described above, but with the two navigation categories combined for 1840), and for 1880 and 1900 for five industrial sectors based on detailed occupational data. Figure 17-3 presents data for the United States by region for 1940, 1970, 2000, and 2010, collapsed down to six major industrial categories to lessen issues of comparability over time.