ABSTRACT
A monopoly situation is defined simply in the traditional theory as a situation where there is a single producer in a given market: a situation in which the essential condition that makes atomistic competition possible is not satisfied. As the quantity demanded of a good changes in a direction opposite to that of a change of price, an increase in the quantity sold by a monopolist producer implies a decline in price. The monopolist does not behave differently from the producer in atomistic competition. When there are a very large number of producers in a market, none of them can influence it. In particular, the selling price remains the same, regardless of the decisions taken by a particular producer. The members of a cartel can certainly have diverging views about the market and a procedure for determining the joint action and the common price is necessary.
