The total revenue curve reflects the degree of market control held by a firm. For a perfectly competitive firm with no market control, the total revenue curve is a straight line. For firms with more market control, especially monopoly, the total revenue curve is "hump shaped," increasing, reaching a peak, then declining. The slope of this total revenue curve is marginal revenue.

Total Revenue Curve, Medicine Style

The total revenue curve for Feet-First Pharmaceutical is displayed in the exhibit to the right. Key to this curve is that Feet-First Pharmaceutical is a monopoly provider of a drug called Amblathan-Plus and thus faces a negatively-sloped demand curve. Larger quantities of output are only possible with lower prices.

The vertical axis measures total 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 curve indicates that if Feet-First Pharmaceutical sells 1 ounce of medicine (at $10 per ounce), then it receives $10 of total revenue. Alternatively, if it sells 10 ounces (at $5.50 per ounce), then it receives $55 of total revenue. Should it sell 12 ounces (at $4.50 per ounce), then it receives only $54 of total revenue.

For Feet-First Pharmaceutical the total revenue "curve" actually is a "curve." The slope of this curve falls as more output is produced, eventually reaching a peak, then becoming negative. The changing slope of this curve is due to the changing price.