While some occupations are found in almost every industry in the United States, some are specific to one or two industries. The Herfindahl-Hirschman index (HHI) provides an index of the occupational concentration by industry.

The concentration of office clerks is at the top with about 2, 808,100 employment. This puts it at a 791 on the HHI. Just under that, at 2,085,680 are secretaries and administrative assistants, excluding legal, medical and executive ones.

At the bottom of the list are computer operators, which have an employment of 71,560 with an HHI of 942 and training and development managers at 27, 350 employment with an HHI of 948.

Find more information by looking at the HHI chart at the Bureau of Labor Statistics.

What it Means

Those occupations which are spread more evenly across industry sectors are measured by low HHIs. Most of the occupations with low HHIs, besides management occupations with broad duties, consisted of general office administration or human resources.

The types of jobs that are related to general office admin include general office clerks; secretaries and administrative assistants except legal, medical and executive; accounting and bookkeeping clerks, and first line supervisors of office and administrative support workers. Over a million were employed in each of these jobs in May 2012.

The human resource positions with low industry concentrations included managerial positions up through the clerical level. This also included training and development managers, human resource managers, training and development specialists and human resource assistants along with payroll and timekeeping clerks.

For jobseekers who value having more mobility, occupations in low concentration industries can provide more flexibility for them to find work in different geographical regions or industries.

Beyond the Numbers

While some industries focus highly on labor that is very specialized, others depend on occupations that are less specialized and that are found widely throughout the economy. While differences in industry staffing patterns could influence the workers' ability to adapt and respond effectively to the economy, occupations that are concentrated in a single industry require very specialized skills. Workers with more widely distributed occupations, however, may move more easily to other occupations in response to a job loss.

This information is based on the Occupational Employment Statistics program.