January 19, 2019 

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OLIGOPSONY: A market structure dominated by a small number of large buyers controlling the buying-side of a market. Oligopsony is the somewhat obscure and seldom discussed buying counterpart to an oligopoly seller that controls the selling side of a market. Whereas oligopoly is most relevant to product markets, oligopsony is most relevant to factor markets.

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Monopoly is a market structure with a single firm selling a unique good. As the only firm on the supply-side of the market, monopoly is a price maker and has extensive market control, facing a negatively-sloped demand curve. If a monopoly wants to sell a larger quantity, then it must lower the price.


Marginal Revenue Curve,
Medicine Style
Marginal Revenue Curve, Monopoly
The marginal revenue curve (MR) for Feet-First Pharmaceutical, a hypothetical firm, is displayed in the exhibit to the right. Key to this curve is that Feet-First Pharmaceutical is a monopoly provider of Amblathan-Plus and thus faces a negatively-sloped demand curve. Larger quantities of output are only possible with lower prices.

The vertical axis measures marginal revenue and the horizontal axis measures the quantity of output (ounces of medicine). Although quantity on this particular graph stops at 12 ounces of medicine, it could go higher.

This exhibit displays both the marginal revenue curve (MR) and the average revenue curve (AR), which is also the demand curve. Both are negatively sloped, but the marginal revenue curve lies below the average revenue curve, which means that marginal revenue is less than average revenue (and price) for any given quantity.

How can this be? Why is this so? An explanation seems in order.

Consider the situation facing the Feet-First Pharmaceutical monopoly. If Feet-First Pharmaceutical sets the Amblathan-Plus price at $8.50, then buyers are willing to purchase 4 ounces. However, if Feet-First Pharmaceutical wants to increase the quantity sold from 4 ounces to 5 ounces, then it MUST lower the price from $8.50 to $8 per ounce as it moves along the demand (average revenue) curve. But here is the catch: Feet-First Pharmaceutical must lower the price for ALL, not just for the fifth ounce.


  • First, by lowering its price, Feet-First Pharmaceutical increases the quantity sold from 4 ounces to 5 ounces. This extra ounce generates an extra $8 of revenue, the price of the sixth ounce. This is $8 of extra revenue that Feet-First Pharmaceutical did NOT have at the higher price. If this is all that happens, then Feet-First Pharmaceutical has a marginal revenue of $8 for the sixth ounce, equal to the price.

  • Second, by lowering its price, Feet-First Pharmaceutical collects less revenue from its other 4 ounces. It would have collected $8.50 per ounce for a total of $34. But with the lower $8 price it collects only $32, a reduction of total revenue by $2, or $0.50 per ounce.

Although this marginal revenue curve is based on the production activity of Feet-First Pharmaceutical, a well-known monopoly firm, it applies to any firm with market control. Monopolistic competition and oligopoly firms that also face negatively-sloped demand curves that generate comparable marginal revenue curves.


Recommended Citation:

MARGINAL REVENUE CURVE, MONOPOLY, AmosWEB Encyclonomic WEB*pedia,, AmosWEB LLC, 2000-2019. [Accessed: January 19, 2019].

Check Out These Related Terms...

     | marginal revenue | marginal revenue, monopoly | marginal revenue curve, perfect competition | marginal revenue curve, monopolistic competition | total revenue curve | average revenue curve | marginal cost curve | marginal product curve | marginal revenue product curve | marginal factor cost curve |

Or For A Little Background...

     | market structures | monopoly | monopoly characteristics | monopoly and demand | perfect competition | oligopoly | monopolistic competition | demand | demand price | law of demand | efficiency |

And For Further Study...

     | short-run production analysis | short-run analysis, monopoly | monopoly and efficiency | breakeven output, monopoly | profit curve, monopoly | short-run production alternatives, monopoly | profit maximization, monopoly |

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