Financial and operating ratios, such as gross profits as a percent of sales, are derived from company financial statements. Ratios are calculated for categories such as liquidity, asset management, debt management, profitability, and market value.
They are used to study changes in a company's operations over time. Ratios for a particular company also are compared with those for the industry as a whole or with those for a specific competitor or group of competitors; the purpose is to identify and then analyze deviations from industry averages.
Some ratio sources arrange data by the North American Industry Classification System (NAICS) or the Standard Industrial Classification System (SIC); the following sources provide details on these two systems:
Financial Analysis Tools and Techniques: a Guide for Managers by 
Business Ratios and Formulas by 
Financial Ratios by 
Finance Basics by 
Financial Statement Analysis by 
Ratios by Some of the sources listed under Financial Ratios - Companies also contain ratios for industries.
