the original and simplified sense, commodities were things of value, of uniform quality, that were produced in large quantities by many different producers; the items from each different producer were considered equivalent. On a commodity exchange, it is the underlying standard stated in the contract that defines the commodity, not any quality inherent in a specific producer's product. Commodities exchanges include: Bourse Africa (formerly GBOT) Bursa Malaysia Derivatives (MDEX) Chicago Board of Trade (CBOT) Chicago Mercantile Exchange (CME) Dalian Commodity Exchange (DCE) Euronext.liffe (LIFFE) Kansas City Board of Trade (KCBT) London Metal Exchange (LME) Marché à Terme International de France (MATIF) Mercantile Exchange Nepal Limited (MEX) Multi Commodity Exchange (MCX) National Commodity and Derivatives Exchange (NCDEX) National Commodity Exchange Limited (NCEL) New York Mercantile Exchange (NYMEX) Markets for trading commodities can be very efficient, particularly if the division into pools matches demand segments. These markets will quickly respond to changes in supply and demand to find an equilibrium price and quantity. In addition, investors can gain passive exposure to the commodity markets through a commodity price index. In order to diversify their investments and mitigate the risks associated with inflationary debasement of currencies, pension funds and sovereign wealth funds allocate capital to non-listed assets such as a commodities and commodity-related infrastructure. Inventory data The inventory of commodities, with low inventories typically leading to more volatile future prices and increasing the risk of a "stockout" (inventory exhaustion). According to economist theorists, companies receive a convenience yield by holding inventories of certain commodities. Data on inventories of commodities are not available from one common source, although data is available from various sources. Inventory data on 31 commodities was used in a 2006 study on the relationship between inventories and commodity futures risk premiums. Commodification of labour In classical political economy and especially in Karl Marx's critique of political economy, a commodity is an object or a good or service ("product" or "activity") produced by human labour. Objects are external to man. However, some objects attain "use value" to persons in this world, when they are found to be "necessary, useful or pleasant in life". "Use value" makes an object "an object of human wants", or "a means of subsistence in the widest sense". As society developed, people found that they could trade goods and services for other goods and services. At this stage, these goods and services became "commodities". According to Marx,