10-K and Annual Report to Shareholders
U.S. public companies must file with the SEC. These reports (10-K, 10-Q, 8-K, Proxies, etc.) are available from several sources. In the Business Overview Section (Item 1 - Business), companies are required to report on the nature of competition in their industry and how they operate within it. This section often delivers key insights into competitive factors and risks that shape an industry.
Note: The glossy "annual report" provided to shareholders is often available on a corporate web site in the Investor Relations section.