Identify the characteristics of a monopolistically competitive market and explain why firms in this market are said to be inefficient. ​

In a monopolistic market there is a large number of small, profit-maximising firms, selling differentiated, heterogeneous products. This means that they have some degree of control of price in the short run, causing a downward sloping demand curve. 

Monopolistically competitive firms are allocatively inefficient. This means that the marginal cost curve is not equal to the average revenue curve at the quantity of production, because of a downward sloping demand (AR) curve. This inefficiency means that there is a deadweight loss, as the marginal benefit to the consumer, shown by the demand curve, is not equal to the marginal cost of production. This is also socially inefficient. 

Firms in this market are also dynamically inefficient. This is because, in the long run, firms do not earn supernormal profits, meaning there is no reinvestment. In turn, there is no reduction in the long run cost curves of firms. 

Firms may be productively efficient but are usually not. This is where marginal costs equal average costs, and the firm is producing at the bottom of the average cost curve, meaning that the firm is producing at minimal cost.