Short Run Production Decision

Short-run decision example

Consider an example of a farmer who is deciding how much corn to plant. The farmer will be selling the corn in a perfectly competitive market where the price is $10 per bushel. The farmer figured that planting corn incurs an opportunity cost of $5, and there are no other fixed costs. However, the farmer's access to water for irrigation is heavily regulated and becomes more costly with each gallon used. Therefore, in our example, the farmer pays an increasing marginal cost for each additional bushel of corn produced.

Table 1. Farmer's Costs for Planting Corn

The farmer maximizes profit by producing up to the point where MR = MC. From our example, we know that the marginal revenue = 10$, so all we have to do is find where marginal cost is equal to 10$ and that is at the quantity level of 4 bushels! So the farmer produces four bushels of corn. Profit is maximized at either three or four bushels of corn, so these two options are equivalent. This tells us that, at four bushels, the marginal revenue of the last unit produced was exactly equal to the marginal cost of producing it.

Types of short-run production decisions

In the current period, which we can think of as the short run, a firm has two decisions to make. The first decision is whether to produce at all, and the second decision is how much to produce. If the answer to the first question is that it is not profitable to produce, then the second question is moot. Thus, the firm actually has two types of short-run production decisions.

• First type: Whether to produce at all
• Second type: What quantity to produce at the given market price

The firm decides whether to produce at all by comparing the given market price to the firm's minimum average variable cost. If the market price is at least as high as the minimum average variable cost, it is profit-maximizing to produce in the current period, even if that means taking a financial loss.

If the market price is below the firm's minimum average variable cost, it is more profitable to shutdown and not produce any units at all. This also means taking a financial loss, but it avoids the even greater loss of producing units that cost more to produce than consumers are willing to pay.

For a given market price, the marginal cost curve itself maps out the firm's optimal quantity for each level of the market price. The individual firm's supply curve, then, is the marginal cost curve—specifically the section that lies above the minimum average variable cost. This section is shown in Figure 2 as a thicker portion of the MC curve. Below the minimum average variable cost, the firm's quantity supplied is zero. Above that point, the quantity supplied is given by the points on the marginal cost curve. Figure 2 shows the individual firm's supply curve and corresponding quantities at three possible market prices.

Fig. 2 - Individual firm's supply curve in perfect competition

Impact of fixed cost on a firm's short-run production decisions

In the short run, some costs are fixed. For example, the compensation of non-hourly workers is fixed regardless of production output. When the firm decides how many units to produce, any fixed costs for the current period are sunk. The size of these fixed costs has no impact on the firm's short-run production decision. Instead, the short-run production decision is based only on the market price and the variable costs (specifically marginal cost and average variable cost).

However, fixed costs can impact the amount of profit that the firm receives at the chosen quantity level. If fixed costs are sufficiently small that the average total cost (at the chosen quantity level) lies below the market price, then the firm is making a profit in the short run. Alternatively, if fixed costs are sufficiently large that the average total cost (at the chosen quantity level) lies above the market price, then the firm is taking a loss in the short run. Taking a loss may still be the profit-maximizing outcome because the fixed costs are already sunk.

Effects of variable cost on short-run production decision

Variable cost is the basis of a firm's short-run production decision. Specifically, the minimum average variable cost determines the firm's shutdown point. If the market price is below the firm's minimum average variable cost, the profit-maximizing quantity for the current period is zero. This is because, at any quantity level, the market price fails to cover the average variable cost of producing the units (not to mention contributing to the fixed costs that have been incurred for the current period).

Firms with higher variable costs will require a higher market price in order to continue producing. For a given market price, a firm with a higher marginal cost will produce a smaller number of units because they produce only up until MR = MC. At the same market price, a firm with a lower marginal cost will produce more units for the same reason.

The firm's minimum average variable cost is the firm's shutdown price. Any price below this would force the firm out of business. Profit-maximizing quantity, in that case, is zero. However, above minimum AVC, the marginal cost curve reveals the firm's profit-maximizing quantity for each given market price. This is why that section of marginal cost is shown with a thicker line in Figure 2. It is the firms' individual supply curve.