Numerous databases are available online listing companies by Standard Industrial Classification or SIC codes and by United States Postal Service ZIP codes. Online lists also allow users to cross-reference these codes with the North American Industry Classification System, or NAICS, codes.
Professional service providers that maintain and charge for their databases compile demographics, trends and marketing reports tailored to the specifications provided. The United States Census Bureau allows users to access information at no charge on its website. Entry of the company classification code allows users to access the most recent census data on companies by region, business type, market size and ZIP code. This database is one of the main resources that the professional service providers use to compile statistics.