There are three main sources for industry information:
Two tips on finding out what industry or industries a company operates in:
Market research reports databases like Mintel and Passport have information on market size.
However, it's not always easy to find size information on a narrow/niche or emerging markets. When that happens, search for Business Source Premier and LexisNexis to see if the info is mentioned in articles. Search websites of relevant industry associations. Google is great at picking up news, blog posts, and press releases that may mention specific numbers.
You may also need to infer from broader market data and come up with your own estimates. Below are two tutorials on how to size a market:
If you don't find market share information in secondary sources such as databases and websites, you may calculate an estimated market share. Divide your company's sales (if your company has only one type of product) or your product's sales (if your company has multiple products) by industry revenue (available in the Economic Census) or industry profiles.