Show the relationships between all the industries in the economy and all the commodities that these industries produce and use. The estimates of purchases of commodities are shown in producers' prices. The I-O accounts consist of the make table, use table, direct requirements table, and total requirements tables. The make and use table are prepared in two different ways. The first way uses the Standard Industrial Classification System (SIC) or the North American Industry Classification System (NAICS). The second way begins with the SIC or NAICS but includes adjustments (redefinitions and reclassifications) that move some secondary products from one industry to another to attain a common input structure for commodities produced by industries. The direct requirements table and total requirements tables are computed from the make and use tables with redefinition and reclassifications.