ECO 306 Intermediate Microeconomics

One measure of competition in an industry is via Concentration Ratios. These generally take 2 forms: 

• the "n-firm" concentration ratio (n=4, 8, 20, 50 firms) 
• the Herfindahl-Hirschman Index (HHI) 

In the U.S., the data is collected and measured by the Census Bureau's Economic Census (available every 5 years only); concentration ratios from the 2017 Economic Census are part of the Establishment and Firm Size data series, which was released beginning in November 2020. 

1) The easiest way to find them is to go to Data.census.gov, and search for "concentration" That should pull up the most recent available tables, now from the 2017 Economic Census (as of Nov 2020), as well as prior years. The 2017 Data is initially available in a report titled: Selected Sectors: Concentration of Largest Firms for the U.S.: 2017.

For the concentration ratio percentages, see the column entitled "Sales, value of shipments, or revenue of largest firms as percent of total sales, value of shipments, or revenue (%)". This shows the CR % for 4,8,20, and 50 firms by NAICS industries from 2 to 6 digits of the hierarchy. The following column will show the Herfindahl-Hirschman Index for the top 50 firms.

For 2012 and prior years, the tables are organized by major NAICS industry groupings, so you should be able to browse for the sector that contains your lower-level industry.  Most industry grouping tables will show the n-firm (4,8, 20, and 50 largest firms) percentages of revenue earned; the Manufacturing tables show the share of "percent of total value of shipments and receipts for services" instead, and also include the Herfindahl-Hirschman Index (HHI) figures for the 50 largest companies.

You will want to use the manufacturing tables for the Percent of the total value of shipments for CR4, 8, 20, 50, and the HHI. The % column is the market share. 

The Economic Census is the U.S. Government's official five-year measure of American business and the economy. It is conducted by the U.S. Census Bureau, and response is required by law. It is conducted in years ending in 2 and 7.  The Economic Census provides rich industry data which is organized by sector based on the North American Industry Classification System (NAICS).

The most efficient way to retrieve data for a particular industry is to search the Explore Census Data search tool or data.census.gov.  This site replaced the previous search tool, the American Factfinder.  

The best way to search is to use the "Advanced Search" feature.  The Census has valuable instructions on building your search using keywords and filters in the  Advanced Search, specifically how to filter by Topic (Business and Economy) and NAICS or industry code.  I would pay close attention to the "Topics" filter, specifically Business & Economy.  You can also apply other filters, such as years, surveys, and codes.  See below for the handy guide explaining how to use these features.  If you are having trouble drilling down to the 6-digit NAICS code, you should take a look. It helped me a lot!

You can also type in your industry code into the search box under "Find a Filter."

If you are getting too few results, try broadening your search and removing/adjusting filters.  Let me know if you are not finding what you need.