Company Statistics Programs
Bureau of Economic Analysis
101 Business Ratios: A Manager's Handbook of Definitions, Equations, & Computer Algorithms: How to Select, Compute, Present, & Understand Measures of Sales, Profit, Debt, Capital, Efficiency, Marketing, & Investment
Economic Census: Concentration Ratios (1992+) "classify industries by the percent of output accounted for by the largest 4, 8, 20 and 50 companies."
Census of Manufactures. Concentration Ratios in Manufacturing