CED

 It is a measure of the responsiveness of demand for one good to a change in price of another good.

 The sign of the value follows: 

Applications of XED

By single business: Coca-cola and Sprite are both produced by the same company. Since they are substitutes, a fall in the price of Sprite will decrease demand for Coca-cola. Should the firm let this happen? First it must have information about the PED for Sprite, so that it can determine whether a price cut will lower or raise total revenue. Then, it must measure the CED to find the degree of substitutability between them. The more positive is it, the greater the decrease in demand for Coca-cola will be.
By rival businesses: A large CED would mean that if Coca-cola increases its price, it would lose a lot of consumers to Pepsi.
Merges: Competitors may decide to merge if they produce close substututes. This is illegal as it reduces competition. Governments should measure CED to ensure merging does not occur with competitor firms.
Complementary goods: A very negative CED means that lowering the price of one good can result in a significant increase in demand and sales for the other. Advantages can be taken from complementarities.