If firms in a monopolistically competitive market are earning positive profits,

The difference between the short‐run and the long‐run in a monopolistically competitive market is that in the long‐run new firms can enter the market, which is especially likely if firms are earning positive economic profits in the short‐run. New firms will be attracted to these profit opportunities and will choose to enter the market in the long‐run. In contrast to a monopolistic market, no barriers to entry exist in a monopolistically competitive market; hence, it is quite easy for new firms to enter the market in the long‐run.

The monopolistically competitive firm's long‐run equilibrium situation is illustrated in Figure .

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Learning Objectives
Monopolistic Competitors and Entry
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What will happen if firms in a monopolistically competitive market are earning positive profits?
When firms currently in a monopolistically competitive market are earning profits?
What happens in a competitive market when there are positive economic profits?
When firms in monopolistic competition earn positive economic profits How will additional firms react?

The entry of new firms leads to an increase in the supply of differentiated products, which causes the firm's market demand curve to shift to the left. As entry into the market increases, the firm's demand curve will continue shifting to the left until it is just tangent to the average total cost curve at the profit maximizing level of output, as shown in Figure . At this point, the firm's economic profits are zero, and there is no longer any incentive for new firms to enter the market. Thus, in the long‐run, the competition brought about by the entry of new firms will cause each firm in a monopolistically competitive market to earn normal profits, just like a perfectly competitive firm.

Excess capacity. Unlike a perfectly competitive firm, a monopolistically competitive firm ends up choosing a level of output that is below its minimum efficient scale, labeled as point b in Figure . When the firm produces below its minimum efficient scale, it is under‐utilizing its available resources. In this situation, the firm is said to have excess capacity because it can easily accommodate an increase in production. This excess capacity is the major social cost of a monopolistically competitive market structure.

Learning Objectives

Explain how short run and long run equilibrium affect entry and exit in a monopolistically competitive industry

Monopolistic Competitors and Entry

A monopolistic competitor, like firms in other market structures, may earn profits in the short run, but that doesn’t mean they’ll be able to keep them. If one monopolistic competitor earns positive economic profits, other firms will be tempted to enter the market. A gas station with a great location must worry that other gas stations might open across the street or down the road—and perhaps the new gas stations will sell coffee or have a carwash or some other attraction to lure customers. A successful restaurant with a unique barbecue sauce must be concerned that other restaurants will try to copy the sauce or offer their own unique recipes. A laundry detergent with a great reputation for quality must be concerned that other competitors may seek to build their own reputations.

The entry of other firms into the same general market (like gas, restaurants, or detergent) shifts the demand curve faced by a monopolistically competitive firm. As more firms enter the market, the quantity demanded at a given price for any particular firm will decline, and the firm’s perceived demand curve will shift to the left. As a firm’s perceived demand curve shifts to the left, its marginal revenue curve will shift to the left, too. The shift in marginal revenue will change the profit-maximizing quantity that the firm chooses to produce, since marginal revenue will then equal marginal cost at a lower quantity.

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Before we dive deeper into an explanation about why firms enter or exit in a monopolistically competitive industry, step through these slides to better understand how changes in demand lead to changes in the market.

Now we’ll step through the above activity in more detail. Figure 1(a) shows a situation in which a monopolistic competitor was earning a profit with its original perceived demand curve (D0). The intersection of the marginal revenue curve (MR0) and marginal cost curve (MC) occurs at point S, corresponding to quantity Q0, which is associated on the demand curve at point T with price P0. The combination of price P0 and quantity Q0 lies above the average cost curve, which shows that the firm is earning positive economic profits.

Figure 1. Monopolistic Competition, Entry, and Exit. (a) At P0 and Q0, the monopolistically competitive firm in this figure is making a positive economic profit. This is clear because if you follow the dotted line above Q0, you can see that price is above average cost. Positive economic profits attract competing firms to the industry, driving the original firm’s demand down to D1. At the new equilibrium quantity (P1, Q1), the original firm is earning zero economic profits, and entry into the industry ceases. In (b) the opposite occurs. At P0 and Q0, the firm is losing money. If you follow the dotted line above Q0, you can see that average cost is above price. Losses induce firms to leave the industry. When they do, demand for the original firm rises to D1, where once again the firm is earning zero economic profit.

Unlike a monopoly, with its high barriers to entry, a monopolistically competitive firm with positive economic profits will attract competition. When another competitor enters the market, the original firm’s perceived demand curve shifts to the left, from D0 to D1, and the associated marginal revenue curve shifts from MR0 to MR1 (as shown in figure 1a). The new profit-maximizing output is Q1, because the intersection of the MR1 and MC now occurs at point U. Moving vertically up from that quantity on the new demand curve, the optimal price is at P1.

As long as the firm is earning positive economic profits, new competitors will continue to enter the market, reducing the original firm’s demand and marginal revenue curves. The long-run equilibrium is shown in the figure at point Y, where the firm’s perceived demand curve touches the average cost curve. When price is equal to average cost, economic profits are zero. Thus, although a monopolistically competitive firm may earn positive economic profits in the short term, the process of new entry will drive down economic profits to zero in the long run. Remember that zero economic profit is not equivalent to zero accounting profit. A zero economic profit means the firm’s accounting profit is equal to what its resources could earn in their next best use. Figure 1(b) shows the reverse situation, where a monopolistically competitive firm is originally losing money. The adjustment to long-run equilibrium is analogous to the previous example. The economic losses lead to firms exiting, which will result in increased demand for this particular firm, and consequently lower losses. Firms exit up to the point where there are no more losses in this market, for example when the demand curve touches the average cost curve, as in point Z.

Monopolistic competitors can make an economic profit or loss in the short run, but in the long run, entry and exit will drive these firms toward a zero economic profit outcome. However, the zero economic profit outcome in monopolistic competition looks different from the zero economic profit outcome in perfect competition in several ways relating both to efficiency and to variety in the market.

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This video demonstrates the graph for a monopolistic competitive firm. In the short run, the graph looks like just like the graph for a monopoly, with the firm making an economic profit. In the long run, however, firms will enter the industry and cause the demand curve to shift to the left, which results in no economic profit.

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These questions allow you to get as much practice as you need, as you can click the link at the top of the first question (“Try another version of these questions”) to get a new set of questions. Practice until you feel comfortable doing the questions.

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What will happen if firms in a monopolistically competitive market are earning positive profits?

If a monopolistically competitive firm is earning positive economic profits, entry will occur until economic profits are equal to zero. The demand curve of a monopolistically competitive firm is downward sloping, indicating that the firm has a degree of market power.

When firms currently in a monopolistically competitive market are earning profits?

As long as firms currently in a monopolistically competitive market are earning profits: more firms will enter the market with products that are close substitutes.

What happens in a competitive market when there are positive economic profits?

Economic profits are the incentive for a firm to enter in a perfectly competitive market. If each firm in a perfectly competitive market is earning a positive economic profit, more firms will enter the market in the long-run. As more firms enter the market in the long-run, the market supply will increase.

When firms in monopolistic competition earn positive economic profits How will additional firms react?

Continuing with the scenario outlined in question 1, in the long run, the positive economic profits earned by the monopolistic competitor will attract a response either from existing firms in the industry or firms outside.