Total Variable Cost Curve

The total variable cost curve can be derived in two ways. One is to plot a schedule of numbers relating output quantity and total variable cost. The other is to vertically subtract the total fixed cost curve from the total cost curve. The slope of this total variable cost curve is marginal cost.

The graph to the right is the total variable cost curve for the short-run production of Wacky Willy Stuffed Amigos (those cute and cuddly armadillos and tarantulas). The quantity of Stuffed Amigos production, measured on the horizontal axis, ranges from 0 to 10 and the total cost incurred in the production of Stuffed Amigos, measured on the vertical axis, ranges from $0 to $43.

The most striking feature of the total variable cost curve is its shape. The total variable cost curve emerges from the origin, then twists and turns its way to $43. This curve begins relatively steep, then flattens, before turning increasingly steep once again. In fact, it is somewhat reminiscent of the total product curve. As a mater of fact, the total variable cost curve can be derived directly from the total product curve.

The slope of the total variable cost curve flattens as the first four Stuffed Amigos are produced. This range of output corresponds with increasing marginal returns found in Stage I of production. Increasing marginal returns causes the total variable cost curve to flatten. The slope of the total variable cost curve becomes increasingly steeper after the fourth Stuffed Amigo is produced. This range of output corresponds with decreasing marginal returns, and the extremely important law of diminishing marginal returns, found in Stage II of production. Deceasing marginal returns causes the total variable cost curve to become steeper.