The value and ton estimates in the Commodity Flow Survey (CFS) represent the sum of multiple shipments of a commodity as it moves through the production and distribution segments of the supply chain. Therefore, CFS totals are much larger than the value added and final weight of materials used in products purchased by consumers and other end users. Also, the total value of shipments, as measured by the CFS, is not directly comparable to the national Gross Domestic Product (GDP), even though both are ostensibly of similar size, because GDP measures the value added or net output of production. The value of goods measured in the CFS includes the market value of goods used in production as well as final demand. Hence, commodities may be counted more than once in the CFS.