The primary goal of most firms is to maximize profit. Other goals, such as maximizing market share or protecting the environment, may also figure into a firm’s mission. But economic models generally start with the assumption that firms attempt to maximize profit. So we will begin with an explanation of how economists define and calculate profit. In the next module we will look at how firms go about maximizing their profit.

In general, a firm’s profit equals its total revenue—which is equal to the price of the output times the quantity sold, or P × Q—minus the cost of all the inputs used to produce its output, its total cost. That is,

Profit = Total Revenue − Total Cost

However, there are different types of costs that may be used to calculate different types of profit. To start the discussion of how to calculate profit, we’ll look at two different types of costs, explicit costs and implicit costs.

Suppose that, after graduating from high school, you have two options: to go to college or to take a job immediately. You would like to continue your education but are concerned about the cost.

What exactly is the cost of attending college? Here it is important to remember the concept of opportunity cost, because the cost of getting a degree includes what you forgo by not taking a job for the years you go to college. The opportunity cost of additional education, like any cost, can be broken into two parts: the explicit cost and the implicit cost.

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An explicit cost is a cost that requires an outlay of money. For example, the explicit cost of a year of college includes tuition. An implicit cost, though, does not involve an outlay of money; instead, it is measured by the value, in dollar terms, of the benefits that are forgone. For example, the implicit cost of a year spent in college includes the income you would have earned if you had taken a job instead.

A common mistake, both in economic analysis and in real business situations, is to ignore implicit costs and focus exclusively on explicit costs. But often the implicit cost of an activity is quite substantial—indeed, sometimes it is much larger than the explicit cost.

Table 52.1 gives a breakdown of hypothetical explicit and implicit costs associated with spending a year in college instead of taking a job. The explicit cost consists of tuition, books, supplies, and a computer for doing assignments—all of which require you to spend money. The implicit cost is the salary you would have earned if you had taken a job instead. As you can see, the forgone salary is $35,000 and the explicit cost is $19,500, making the implicit cost more than the explicit cost in this example. So ignoring the implicit cost of an action can lead to a seriously misguided decision.

A slightly different way of looking at the implicit cost in this example can deepen our understanding of opportunity cost. The forgone salary is the cost of using your own resources—your time—in going to college rather than working. The use of your time for more education, despite the fact that you don’t have to spend any money, is still costly to you. This illustrates an important aspect of opportunity cost: in considering the cost of an activity, you should include the cost of using any of your own resources for that activity. You can calculate the cost of using your own resources by determining what they would have earned in their next best alternative use.

As the example of going to college suggests, taking account of implicit as well as explicit costs can be very important when making decisions. This is true whether the decisions affect individuals, groups, governments, or businesses.

Consider the case of Babette’s Cajun Café, a small restaurant in New Orleans. This year Babette brought in $100,000 in revenue. Out of that revenue, she paid her expenses: the cost of food ingredients and other supplies, the cost of wages for her employees, and the rent for her restaurant space. This year her expenses were $60,000. We assume that Babette owns her restaurant equipment—items such as appliances and furnishings. The question is: Is Babette’s restaurant profitable?

At first it might seem that the answer is obviously yes: she receives $100,000 from her customers and has expenses of only $60,000. Doesn’t this mean that she has a profit of $40,000? Not according to her accountant, who reduces the number by $5,000 for the yearly depreciation (reduction in value) of the restaurant equipment. Depreciation occurs because equipment wears out over time. As a consequence, every few years Babette must replace her appliances and furnishings. The yearly depreciation amount reflects what an accountant estimates to be the reduction in the value of the machines due to wear and tear that year. This leaves $35,000, which is the business’s accounting profit. That is, the accounting profit of a business is its total revenue minus its explicit cost and depreciation. The accounting profit is the number that Babette has to report on her income tax forms and that she would be obliged to report to anyone thinking of investing in her business.

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Accounting profit is a very useful number, but suppose that Babette wants to decide whether to keep her restaurant open or to do something else. To make this decision, she will need to calculate her economic profit—the total revenue she receives minus her opportunity cost, which includes implicit as well as explicit costs. In general, when economists use the simple term profit, they are referring to economic profit. (We adopt this simplification in this book.)

Why does Babette’s economic profit differ from her accounting profit? Because she may have an implicit cost over and above the explicit cost her accountant has calculated. Businesses can face an implicit cost for two reasons. First, a business’s capital—its equipment, buildings, tools, inventory, and financial assets—could have been put to use in some other way. If the business owns its capital, it does not pay any money for its use, but it pays an implicit cost because it does not use the capital in some other way. Second, the owner devotes time and energy to the business that could have been used elsewhere—a particularly important factor in small businesses, whose owners tend to put in many long hours.

If Babette had rented her appliances and furnishings instead of owning them, her rent would have been an explicit cost. But because Babette owns her own equipment, she does not pay rent on it and her accountant deducts an estimate of its depreciation in the profit statement. However, this does not account for the opportunity cost of the equipment—what Babette forgoes by owning it. Suppose that instead of using the equipment in her own restaurant, the best alternative Babette has is to sell the equipment for $50,000 and put the money into a bank account where it would earn yearly interest of $3,000. This $3,000 is an implicit cost of running the business. The implicit cost of capital is the opportunity cost of the capital used by a business; it reflects the income that could have been earned if the capital had been used in its next best alternative way. It is just as much a true cost as if Babette had rented her equipment instead of owning it.

Finally, Babette should take into account the opportunity cost of her own time. Suppose that instead of running her own restaurant, she could earn $34,000 as a chef in someone else’s restaurant. That $34,000 is also an implicit cost of her business.

Table 52.2, in the column titled Case 1, summarizes the accounting for Babette’s Cajun Café, taking both explicit and implicit costs into account. It turns out, unfortunately, that although the business makes an accounting profit of $35,000, its economic profit is actually negative. This means that Babette would be better off financially if she closed the restaurant and devoted her time and capital to something else. If, however, some of Babette’s cost should fall sufficiently, she could earn a positive economic profit. In that case, she would be better off financially if she continued to operate the restaurant. For instance, consider the column titled Case 2: here we assume that what Babette could earn as a chef employed by someone else has dropped to $30,000 (say, due to a soft labor market). In this case, her economic profit is positive: she is earning more than her explicit and implicit costs and she should keep her restaurant open.

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In real life, discrepancies between accounting profit and economic profit are extremely common. As the FYI above explains, this is a message that has found a receptive audience among real-world businesses.

In the example above, when Babette is earning an economic profit, her total revenue is higher than the sum of her implicit and explicit costs. This means that operating her restaurant makes Babette better off financially than she would be using her resources in any other activity. When Babette earns a negative economic profit (which can also be described as a loss), it means that Babette would be better off financially if she devoted her resources to her next best alternative. As this example illustrates, economic profits signal the best use of resources. A positive economic profit indicates that the current use is the best use of resources. A negative economic profit indicates that there is a better alternative use for resources.

But what about an economic profit equal to zero? Most of us would generally think earning zero profit was a bad thing. After all, a firm’s goal is to maximize profit—profit is what firms are after! However, an economic profit equal to zero is not bad at all. An economic profit of zero means that the firm could not do any better using its resources in any alternative activity. Another name for an economic profit of zero is a normal profit. A firm earning a normal profit is earning just enough to keep it using its resources in its current activity. After all, it can’t do any better in any other activity! In Module 59 we’ll see that firms earning negative economic profit can sometimes minimize their losses by staying open for a while, but all such firms will close in the long run unless conditions change.