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July / August 2010
Volume 22, Number 4

Data about counties, by Tim Brown

Industries with the Most Employees

Every year, the U. S. Census Bureau publishes data on the number of employees in each industry and the total payroll in each county. In addition to the totals, the Bureau provides detailed data allowing anyone to drill down to a varying level of detail. The level depends on several factors, but the two most important ones are the uniformity of the industry and how well the particular levels of detail are represented within the county.

The first factor is pretty straightforward; the more differences there are within a particular industry, the more it must be divided up in the survey results. The Bureau uses the standard North American Industry Classification System (NAICS) to identify companies by industry. NAICS is surprisingly detailed; the 2007 index file lists more than 19,000 different classifications. Anyone interested in some light reading can purchase the book online at Amazon for only $59; the 1,392-page book weighs only 3.8 pounds.

The second factor isn’t as obvious at first. In order to avoid disclosing data from individual companies, the Bureau introduces a random multiplier for much of the data at the detailed levels.

This is usually not a problem for larger counties that have well represented cross-sections of industry. It is a problem for small counties or counties where only a small number of companies exist within a specific industry. When the number of such companies is very small, the data is withheld entirely. This impacts the maps since the Bureau provides no data, even at a high level, for three counties: Borden, King and Loving.

The first map shows the industry with the greatest number of employees in each county. For example, there are more employees in the Retail Sales industry in El Paso than in any other industry in 2007. Curiously, Retail Sales dominated in 86 counties (statewide, there were 1,156,454 employees this field). Farming and ranching, part of the Forestry, Fishing, Hunting and Agriculture Support industry, was the primary employer in only one county – Glasscock.

The second map shows the industry with the most employees if one ignores the Retail Sales industry. By eliminating Retail Sales from the analysis, Health Care and Social Assistance becomes the dominant employer in 95 counties. This is not unexpected, as there are 1,150,715 employees in this field statewide. Between them, the two fields accounted for just over 25 percent of all employees in the state.