HOW A FIRM ARRIVES AT A PROFIT-MAXIMIZING POINT
Let us assume throughout the discussion that a firm uses an economist's definition of profits. Assume that profit is the excess of sales revenue over cost (now assumed to be composed of both explicit and implicit costs). It can also be assumed, as discussed above, that the profit maximization is the firm's primary goal. Given this objective, important questions remain: How does the firm decide on the output level that maximizes its profits? Should the firm continue to produce at all if it is not profitable? A manufacturing firm, motivated by profit maximization, calculates the total cost of producing any given output level. The total cost is made up of total fixed cost (due to the expenditure on fixed inputs) and total variable cost (due to the expenditure on variable inputs). Of course, the total fixed cost does not vary over the short runnly the total variable cost does. It is important for the firm to also calculate the cost per unit of output, called the average cost. In addition to the average cost, the firm calculates the marginal cost. The marginal cost at any level of output is the increase in the total cost due to an increase in production by one unitssentially, the marginal cost is the additional cost of producing the last unit of output. The average cost is made up of two components: the average fixed cost (the total fixed cost divided by the number of units of the output produced) and the average variable cost (the total variable cost divided by the number of units of the output produced). As the fixed costs remain fixed over the short run, the average fixed cost declines as the level of production increases. The average variable cost, on the other hand, first decreases and then increases; economists refer to this as the U-shaped nature of the average variable cost. The U-shape of the average variable cost curve is explained as follows. Given the fixed inputs, output of the relevant product increases more than proportionately as the levels of variable inputs used increase. This is caused by increased efficiency due to specialization and other reasons. As more and more variable inputs are used in conjunction with the given fixed inputs, however, efficiency gains reach a maximumhe decline in the average variable cost eventually comes to a halt. After this point, the average variable cost starts increasing as the level of production continues to increase, given the fixed inputs. First decreasing and then increasing average variable cost lead to the U-shape for the average variable cost. The combination of the declining average fixed cost (true for the entire range of production) and the U-shaped average variable cost results into an U-shaped behavior of the average total cost, often simply called the average cost. The marginal cost also displays a U-shaped patternt first decreases and then increases. The logic for the shape of the marginal cost curve is similar to that for the average variable costoth relate to variable costs. But while the marginal cost refers to the increase in total variable cost due to an increase in the production by one unit, the average variable cost refers to the average variable cost per unit of output produced. It is important to notice, without going into finer details, that the marginal cost curve intersects the average and the average variable cost curves at their minimum cost points. In a graphic rendering of this concept there would be a horizontal line, in addition to the three cost curves. It is assumed that the firm can sell as many units as it wants at the given market price indicated by this horizontal line. Essentially, the horizontal line is the demand curve a perfectly competitive firm faces in the markett can sell as many units of output as it deems profitable at price "p" per unit (p, for example, can be $10 per unit of the product under consideration). In other words, p is the firm's average revenue per unit of output. Since the firm receives p dollars for every successive unit it sells, p is also the marginal revenue for the firm. A firm maximizes profits, in general, when its marginal revenue equals marginal cost. If the firm produces beyond this point of equality between the marginal revenue and marginal cost, the marginal cost will be higher than the marginal revenue. In other words, the addition to total production beyond the point where marginal revenue equals marginal cost, leads to lower, not higher, profits. While every firm's primary motive is to maximize profits, its output decision (consistent with the profit maximizing objective), depends on the structure of the market it is operating under. Before we discuss important market structures, we briefly examine another key economic concept, the theory of consumer behavior.