This refers to a situation where the supply of two or more goods is inextricably linked. The increase or decrease in the supply of one of the goods will cause the supply of the other good to also increase or decrease at the same time. The increase in the supply of cows, for instance, simultaneously increases the supply of both milk as well as meat in the market. So the prices of both milk and meat will be affected by the rearing of more cows by farmers. The demand for jointly supplied goods, however, may not be commensurate with the available supply of each of the goods. The demand for milk, for instance, may be greater than the demand for meat in certain markets.