Monopolistic Competition: Long-Run Equilibrium

1. From Short-Run Profit to Long-Run Competition

The story of the long run begins with the success of the short run. When existing firms earn positive economic profits, it acts as a powerful signal to the market.

Remember two key characteristics of monopolistic competition:

• There are a large number of firms.
• Barriers to entry and exit are low.

Because it's relatively easy for new companies to enter, the economic profits earned by existing firms attract new competitors. Imagine a neighborhood where a single, highly profitable boutique coffee shop opens. It won't be long before other entrepreneurs notice this success and decide to open their own coffee shops nearby.

What is the impact on the original coffee shop?

1. Demand Decreases: Some of its customers will be lured away by the new alternatives. This causes the demand curve for the original firm's product to shift to the left.
2. Demand Becomes More Elastic: With more substitutes available, customers become more price-sensitive. A small price increase by the original shop is now more likely to send customers to a competitor. This makes the firm's demand curve flatter (more elastic).

This process of entry continues as long as there are economic profits to be made.

The following reading provides a clear, CFA-focused explanation of this dynamic.

2. The Long-Run Equilibrium Graph

This process of new firms entering and demand shifting left continues until economic profit is eliminated. This occurs when the firm's demand curve becomes tangent to its Average Total Cost (ATC) curve. At this point, the price the firm can charge for its profit-maximizing quantity is exactly equal to the average cost of producing it.

Since Profit per unit = Price - ATC, if P = ATC, the profit per unit is zero, and thus the total economic profit is zero. The firm is now earning only a normal profit—just enough to cover its explicit and implicit costs.

Drawing this long-run equilibrium graph can be tricky. The following video provides an excellent step-by-step guide to constructing it correctly, showing the dynamic shift that leads to the final equilibrium.

Here is a clear, static image of the final long-run equilibrium.

Key features to note in the long-run equilibrium:

• The firm still follows the profit-maximization rule: MR = MC.
• Demand has shifted leftward so that at the profit-maximizing quantity (Qmc), Price = Average Total Cost (Pmc = AC).
• Economic profit is zero. There is no longer an incentive for new firms to enter, and the market is stable.

3. Efficiency Implications: A Trade-Off

Is the long-run outcome in monopolistic competition efficient? To answer this, economists compare it to the benchmark of perfect competition. We find that monopolistic competition is neither allocatively nor productively efficient.

1. Productive Inefficiency and Excess Capacity

• Productive efficiency occurs when a good is produced at the lowest possible cost, which is the minimum point of the Average Total Cost (ATC) curve.
• Looking at the graph above, you can see the firm produces at quantity Qmc, which is on the downward-sloping portion of the ATC curve. It is not producing at the minimum of the ATC curve (which occurs at Qpc).
• This difference between the profit-maximizing quantity (Qmc) and the productively efficient quantity (Qpc) is called excess capacity. The firm has the capacity to produce more and lower its average cost, but it doesn't because to sell those extra units, it would have to lower its price on all units, leading to a loss.

2. Allocative Inefficiency

• Allocative efficiency occurs when resources are used to produce the goods and services most desired by society. This happens when price equals marginal cost (P = MC).
• In our long-run equilibrium graph, the firm charges price Pmc, which is determined by the demand curve. This price is greater than the marginal cost (MC) at that level of output.
• Because P > MC, it means consumers value the last unit produced more than it cost to make. From society's perspective, more should be produced. This gap represents a degree of inefficiency, leading to a deadweight loss (though smaller than in a pure monopoly).

The following reading provides another look at this long-run outcome and the comparison with perfect competition.

So, if monopolistic competition is inefficient, what do we get in return? The answer lies in its defining feature: product differentiation. The "inefficiency" is the price we pay for variety—the choice between different styles of clothing, types of restaurants, and brands of coffee. While a perfectly competitive market would give us one generic product at the lowest possible price, monopolistic competition gives us variety, innovation, and branding, which many consumers value.

4. Practice Question

Let's check your understanding of the key conditions in this long-run equilibrium.

Question:

In the long-run equilibrium of a monopolistically competitive market, which of the following statements is most accurate?

1. Firms produce at the minimum point of their average total cost curve.
2. Price is equal to marginal cost.
3. Firms earn positive economic profits due to product differentiation.
4. Price is equal to average total cost but is greater than marginal cost.

Conclusion

This lesson traced the path from short-run profitability to long-run equilibrium in monopolistic competition. The lure of profits in a market with low entry barriers is the catalyst for change, ultimately leading to a stable but inefficient outcome.

Key Takeaways:

• Short-run economic profits attract new entrants into a monopolistically competitive market.
• The entry of new firms shifts the demand curve for existing firms to the left, making it more elastic.
• This process continues until economic profits are competed away, and firms earn only a normal profit.
• The long-run equilibrium occurs at the quantity where MR = MC, and where the demand curve is tangent to the ATC curve, such that P = ATC.
• The long-run outcome is inefficient:
  • Productively inefficient: Firms have excess capacity (P > minimum ATC).
  • Allocatively inefficient: Price is a markup over marginal cost (P > MC).
• The "cost" of this inefficiency is offset by the benefit of product variety and innovation.

Preview of the Next Lesson:

We have now analyzed market structures with many firms (perfect and monopolistic competition). In the next module, we will shift to the other extreme of the market structure spectrum. We will begin by examining monopoly, a market dominated by a single seller, where high barriers to entry allow for the possibility of sustained long-run economic profits.