Why is there so much advertising in monopolistic competition and oligopoly? How does such advertising help consumers and promote efficiency? Why might it be excessive at times?

In monopolistic competition, advertising is used to accomplish product differentiation and to control the market. Through advertising, a company can inform the targeted market about the physical differences of the products they are offering. This helps the firm to control the market activities.

In an oligopoly, advertising helps to ensure the customer do not shift to other firms who have competing products.

Advertising helps the consumers in knowing about the availability of a product and other information about the goods. It helps in promoting efficiency by encouraging firms to produce more of their products.

At times, advertising may be excessive where it becomes persuasive other than informative.