zero elasticity of demand

no market power

independence among the few firms

products that are always standardized

Relatively easy entry and exit 

A potential for price-fixing through collusion

A doctor charges for services according to the income of

patients.

An electric power company charges less for electricity used

during hours when production costs are lower.

Universities charge higher tuition for out-of-state residents.

A theater charges children less than adults for a movie.

Marginal revenue = Demand.

Marginal cost = Demand.

Average total cost = Demand.

Marginal cost = Marginal revenue.

charging lower prices to customers wearing a Heaters t-shirt

charging lower prices during happy hour

charging higher prices than under perfect competition

charging higher prices for imported beer than domestic beer

on rare occasions, rival firms may enter the industry, but exiting may be difficult.

on rare occasions, the monopolist may need to advertise to differentiate its product

the monopolist produces a product with no close substitutes.

on rare occasions, the monopolist may be seen as a price taker.

advertising only exists in pure competition

there is some control over price in monopolistic competition

products can be standardized or differentiated in perfect competition 

collusion only exists in pure competition