The survey, which was sent to 2.3 million business owners based on 2007 tax returns, shows that the 78.8 percent of businesses without employees account for 3.2 percent of sales, with an average of a little more than $45,000.

Of those with employees, the average sales is over $5 million, with an average of 20 employees per business.

The share of businesses without employees now exceeds 90 percent in agriculture and arts, entertainment and recreation. The only sector of the economy where the majority of businesses has employees is accommodation and food services, in which 61.5 percent of businesses still have workers.

The largest share of American companies is in the professional, scientific, and technical services sector, which accounts for 14.0 percent of U.S. companies. Construction accounts for the next highest portion at 12.6 percent. Manufacturing and agriculture, once the mainstays of American business, now account for 2.3 and 1.0 percent of U.S. companies, respectively. See an overview of the report.

The full report with detailed information on demographics, geography, industry, sales, and employees is available through the Census survey website.