What are the top 10 biggest U.S. industries by percentage?

Question

for example :
oil and gas 32%
finacials 27%

Answer 1

By percentage of what? Workers employed? Contribution to GDP? Something else?

Data about GDP by industry can be found here:

http://www.bea.gov/industry/gpotables/gpo_action.cfm?anon=52381&table_id=19019&format_type=0

For employment by industry data, start here:

http://www.bls.gov/ces/home.htm

__________

Answer 2

Of course the answer will depend on what you mean by biggest and what you mean by industry. There are at least three ways to measure the size of an industry -- sales revenue, value added, and employment.

Value added (the difference between total sales revenues and the cost of inputs bought from other industries) is probably the best. For example, Wal Mart looks huge if measured by sales revenue, but its value added is much smaller. The value added by a retailer is only the difference between the sales price for an item in the store and what the retailer paid for it from the wholesaler'

A common way to define an industry is the North American Industry Classification System. It starts off with 12 super industries which are each given a two digit code. Each two digit industry is further divided into a number of smaller three digit industries. Each three digit industry is further divided into four digit industries. The smallest industry classification has six digits.

For example, oil and gas extraction is a three digit industry under the two digit industry of mining. Petroleum refining, however, is a separate industry under the two digit industry of manufacturing.