Requirements tables are prepared for analytical uses of the benchmark I-O accounts, and are derived from the make and use table. There are two types of tables, direct requirements and total requirements, which are produced in coefficient form. Direct requirements coefficients show the amount of inputs purchased directly to produce one dollar of output. Total requirements coefficients show the sum of direct and indirect purchases required to produce a dollar of output. Indirect purchases necessary to produce an automobile, for example, would include the aluminum used in the frame and engine, as well as the electricity necessary to produce the aluminum. Four types of direct and total requirements tables are possible, depending on whether the rows and columns of the tables are defined to be commodities or industries. However, some commonly used tables are calculated and made available by BEA to its users. These include: 1) the commodity by industry direct requirements table, which can be used to calculate the commodity inputs required directly for a dollar of industry output; 2) the industry by industry total requirements table, used to calculate total industry requirements for a dollar of industry output; 3) the industry by commodity total requirements table, used to calculate total industry requirements for a dollar of commodity output; and 4) the commodity by commodity total requirements table, used to calculate total commodity requirements for a dollar of commodity output. A more comprehensive explanation of these tables can be found in “Concepts and Methods of the U.S. Input-Output Accounts,” at http://www.bea.gov/papers/pdf/IOmanual_092906.pdf, and in “MEASURING THE NATION’S ECONOMY: AN INDUSTRY PERSPECTIVE, A Primer on BEA’s Industry Accounts” (Revised May 2011), at http://www.bea.gov/industry/pdf/industry_primer.pdf
The downloadable files for the 2002, 1997, 1992 and earlier tables include a short document which presents the matrix algebra describing the calculation of the various types of requirements tables from the original make and use tables.