What is Marginal Revenue and Marginal Cost for a Monopolist?

In the real world, a monopolist often does not have enough information to analyze its entire total revenues or total costs curves. After all, the firm does not know exactly what would happen if it were to alter production dramatically. However, a monopolist often has fairly reliable information about how changing output by small or moderate amounts will affect its marginal revenues and marginal costs, because it has had experience with such changes over time and because modest changes are easier to extrapolate from current experience. A monopolist can use information on marginal revenue and marginal cost to seek out the profit-maximizing combination of quantity and price.

This monopoly faces typical upward-sloping marginal cost and downward sloping marginal revenue curves.

For a perfect competitor, each additional unit sold brought a positive marginal revenue, because marginal revenue was equal to the given market price. 

However, a monopolist can sell a larger quantity and see a decline in total revenue. 

When a monopolist increases sales by one unit, it gains some marginal revenue from selling that extra unit, but also loses some marginal revenue because it must now sell every other unit at a lower price. As the quantity sold becomes higher, at some point the drop in price is proportionally more than the increase in greater quantity of sales, causing a situation where more sales bring in less revenue. In other words, marginal revenue is negative.

The profit-maximizing choice for the monopoly will be to produce at the quantity where marginal revenue is equal to marginal cost: that is, MR = MC. If the monopoly produces a lower quantity, then MR > MC at those levels of output, and the firm can make higher profits by expanding output. If the firm produces at a greater quantity, then MC > MR, and the firm can make higher profits by reducing its quantity of output.

A monopolist can determine its profit-maximizing price and quantity by analyzing the marginal revenue and marginal costs of producing an extra unit. If the marginal revenue exceeds the marginal cost, then the firm should produce the extra unit.

The monopoly could seek out the profit-maximizing level of output by increasing quantity by a small amount, calculating marginal revenue and marginal cost, and then either increasing output as long as marginal revenue exceeds marginal cost or reducing output if marginal cost exceeds marginal revenue. This process works without any need to calculate total revenue and total cost. Thus, a profit-maximizing monopoly should follow the rule of producing up to the quantity where marginal revenue is equal to marginal cost—that is, MR = MC. This quantity is easy to identify graphically, where MR and MC intersect.

 A perfectly competitive firm will also find its profit-maximizing level of output where MR = MC. The key difference with a perfectly competitive firm is that in the case of perfect competition, marginal revenue is equal to price (MR = P), while for a monopolist, marginal revenue is not equal to the price, because changes in quantity of output affect the price.

Related Topics

• Market Structure
• Perfect Competition
• Bidding War
• Complements & Substitutes
• Substitution Effect
• Imperfect Competition
• Market Power
• Price Takers
• Price Makers 
• Perfect Competition and Decision Making
• X-Efficiency
• Captive Market
• Contestable Market Theory
• Highest Profit Point in a Perfectly Competitive Market
• Marginal Revenue
• Using Marginal Revenue and Marginal Costs to Maximize Profit
• Marginal Revenue Curve
• Profit Margin and Average Total Cost
• Break Even Point - Cost Curve
• Shutdown Point - Cost Curve
• Short-Run Decisions Based Upon Costs in a Perfectly Competitive Market
• Marginal Costs and the Supply Curve for a Perfectively Competitive Firm
• Long-Run Average Supply (LRAS)
• Decisions to Enter or Exit a Market in the Long Run
• Long-Run Equilibrium in a Perfectly Competitive Market
• Constant, Increasing, and Decreasing Cost Industries
• Productive and Allocative Efficiency in Perfectly Competitive Markets
• Market Efficiency
• Market Inefficiency
• Pareto Efficiency
• Market Failure 
• Search Theory
• Monopoly
• Natural Monopoly
• Legal Monopoly
• Bilateral Monopoly
• Promoting Innovation through Intellectual Property
• Predatory Pricing
• How Monopolists Set Price with the Demand Curve
• Total Cost and Total Revenue for a Monopolist
• Marginal Revenue and Marginal Cost for a Monopolist
• Inefficiency of Monopoly
• Perfectly Competitive Market
• Monopolistic Competition
• Duopoly
• Oligopoly
• Differentiated Products
• Perceived Demand for a Monopolistic Competitor
• Monopolistic Competitors Choose Price and Quantity
• Monopolistic Competitors and Entry
• Monopolistic Competition and Efficiency
• Cartel (Economics)
• Game Theory
• Traveler's Dilemma
• Prisoner's Dilemma
• Iterated Prisoner's Dilemma
• Nash Equilibrium
• Diner's Dilemma
• Trembling Hand Perfect Equilibrium
• Gambler's Fallacy
• Arrows Impossibility Theorem
• Backward Induction
• Tournament Theory
• Oligopoly and the Prisoner’s Dilemma
• Forcing Cooperation in a Prisoner’s Dilemma
• Cooperation and the Kinked Demand Curve
• Corporate Merger or Acquisition
• Antitrust Laws
• Herfindahl-Hirschman Index
• Concentration Ratio
• Other Approaches to Measuring Monopoly Power in an Industry
• Restrictive Practices under Antitrust Law
• Natural Monopoly
• Cost-Plus Regulation
• Price Cap Regulation
• Regulatory Capture