In economics

Economics

Economics is the social science that analyzes the production, distribution, and consumption of goods and services. The term economics comes from the Ancient Greek from + , hence "rules of the house"...

, joint demand is a kind of demand

Demand

- Economics :*Demand , the desire to own something and the ability to pay for it*Demand curve, a graphic representation of a demand schedule*Demand deposit, the money in checking accounts...

 that occurs when the demand for two or more products (or services) are interdependent, normally because they are used together. The demand for razor blades may depend upon the number of razors in use; this is why razors have sometimes been sold as loss leader

Loss leader

A loss leader or leader is a product sold at a low price to stimulate other profitable sales. It is a kind of sales promotion, in other words marketing concentrating on a pricing strategy. A loss leader is often a popular article...

s, to increase demand for the associated blades.

There is some similarity to the concept of derived demand

Derived demand

Derived demand is a term in economics, where demand for one good or service occurs as a result of demand for another. This may occur as the former is a part of production of the second. For example, demand for coal leads to derived demand for mining, as coal must be mined for coal to be consumed....

.