8.3 : 完全競争におけるMR（限界収益）

A firm's revenues can be measured as total, average, and marginal revenue.

Consider a perfectly competitive market where James, the wheat producer, has put a hundred bushels of wheat for sale at the prevailing market price of six dollars per bushel.

Total Revenue is the total income a firm receives from selling a given quantity of output.

If James sells everything, his total revenue would be six hundred dollars.

Average Revenue is the per-unit income, calculated by dividing Total Revenue by quantity sold. James's average revenue equals six dollars per bushel, which is also the selling price.

Marginal Revenue denotes the extra income generated by selling an additional unit. Marginal Revenue is always equivalent to the market price in a perfectly competitive market. For James, it will be six dollars per extra bushel.

This shows that in perfect competition, Average Revenue, Marginal Revenue, and Market Price will be the same, also depicted by the horizontal demand curve.

This also proves that a firm is a price-taker in a perfectly competitive market.