April 23, 2018 

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A curve that graphically represents the relation between the marginal cost incurred by a firm in the short-run product of a good or service and the quantity of output produced. This curve is constructed to capture the relation between marginal cost and the level of output, holding other variables like technology and resource prices constant. Three related curves are average total cost curve, average variable cost curve, and average fixed cost curve.
The marginal cost curve, the graphical relation between marginal cost and output, is U-shaped. Marginal cost is relatively high at small quantities of output, then as production increases, it declines, reaches a minimum value, then rises once again.

This U shape is directly attributable to increasing, then decreasing marginal returns (and the law of diminishing marginal returns). As marginal product (and marginal returns) increases for relatively small output quantities, marginal cost declines. Then as marginal product (and marginal returns) decreases with the law of diminishing marginal returns for relatively large output quantities, marginal cost increases.

Marginal Cost Curve
Marginal Cost Curve
The graph presented at the right is the marginal cost curve for the short-run production of Wacky Willy Stuffed Amigos (those cute and cuddly scorpions and turtles). The quantity of Stuffed Amigos production, measured on the horizontal axis, ranges from 0 to 10 and the marginal cost incurred in the production of Stuffed Amigos, measured on the vertical axis, starts at $5, declines to $1.50, then rises again to $12.

The marginal cost curve is U-shaped. For the first 4 Stuffed Amigos, marginal cost declines from $5 to a low of $1.50. However, for the production beyond 6 Stuffed Amigos, marginal cost increases. The source of this U-shaped marginal cost curve rests with increasing and decreasing marginal returns. In fact, the negatively-sloping portion of the marginal cost curve coincides exactly with increasing marginal returns in production Stage I. The positively-sloping portion of the marginal cost curve coincides exactly with decreasing marginal returns in production Stage II.

The marginal cost curve takes center stage in the analysis of a firm's short-run production. In particular, a profit-maximizing firm equates the marginal revenue received from selling a good with the marginal cost of producing it. For a firm operating under perfect competition, its marginal cost curve becomes its supply curve. The marginal cost curve, because it measures the incremental opportunity cost of producing one more unit of a good plays, an important role in analyzing the efficient allocation of resources.


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Check Out These Related Terms...

     | marginal cost | average cost | total cost | total variable cost | total fixed cost | average total cost | average fixed cost | average variable cost | variable cost | fixed cost | total cost curve | total fixed cost curve | total variable cost curve | average total cost curve | average fixed cost curve | average variable cost curve | U-shaped cost curves |

Or For A Little Background...

     | opportunity cost | production | production cost | business | factors of production | microeconomics | short-run production analysis | law of diminishing marginal returns | marginal returns | marginal analysis | marginal product | total-marginal relation |

And For Further Study...

     | marginal cost and law of diminishing marginal returns | marginal cost and marginal product | total cost and marginal cost | total cost curves | total variable cost and total product | legal business organizations | firm objectives | opportunity cost, production possibilities | profit | economic profit | accounting profit | normal profit | accounting cost | profit maximization | long-run marginal cost |

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