Competition can be "imperfect" in an industry if the industry deviates from any one of the four. So, if there are just a few firms (but more than one), deviating from the first characteristic, the industry is said to be an "oligopoly." Since the nineteen-twenties, economists have also discussed the situation when an "industry" deviates only in the second characteristic. This is called "monopolistic competition," and we have "monopolistic competition" when a group of firms sell closely related, but not homogenous products. Instead, the products are said to be "differentiated products." So, the characteristics of "monopolistic competition" are:

To say that products are differentiated is to say that the products may be (more or less) good substitutes, but they are not perfect substitutes. For

• A reduction in demand leads to a reduction in both price and output. However we have to investigate the effects on profit to determine if this is a long run equilibrium.

Some topics in this essay:
Monopolistic Competition, Friends Frasier, Inefficiency Notice, George Stigler, Downtown Aventura, Sprite Squirt, United Germany, Downtown Miami, Downtown Hairdressers', Imperfect Competition, monopolistic competition, run equilibrium, monopolistically competitive, free entry, competitive industry, product differentiation, perfect competitive, competitive firm, perfect substitutes, differentiated products, monopolistically competitive industry, monopolistically competitive firm, perfect competitive industry, products differentiated products, revenue curves shifting,