A key concept in conducting industry research is the classification of economic activity. Two systems are used: Standard Industrial Classification (SIC) and North American Industry Classification System (NAICS). Although NAICS has replaced SIC, some publications and resources still use SIC (or both!).
These resources give solid overviews of industries and markets, with current trends and analysis. These resources will help you answer the questions: What is the current value of the industry? Is the industry growing? What are the major companies/competitors in the industry and what is their market share? What are some barriers to entry or threats to the industry?