Economic equilibrium

In economics, economic equilibrium is a state where economic forces such as supply and demand are balanced and in the absence of external influences the (equilibrium) values of economic variables will not change. For example, in the standard text-book model of perfect competition, equilibrium occurs at the point at which quantity demanded and quantity supplied are equal.^[1] Market equilibrium in this case refers to a condition where a market price is established through competition such that the amount of goods or services sought by buyers is equal to the amount of goods or services produced by sellers. This price is often called the competitive price or market clearing price and will tend not to change unless demand or supply changes and the quantity is called "competitive quantity" or market clearing quantity.

Properties of equilibrium

Three basic properties of equilibrium in general have been proposed by Huw Dixon.^[2] These are:

Equilibrium property P1: The behavior of agents is consistent.

Equilibrium property P2: No agent has an incentive to change its behavior.

Equilibrium Property P3: Equilibrium is the outcome of some dynamic process (stability).

Normal profit

Normal profit is a component of (implicit) costs and not a component of business profit at all. It represents the opportunity cost, as the time that the owner spends running the firm could be spent on running a different firm. The enterprise component of normal profit is thus the profit that a business owner considers necessary to make running the business worth her or his while i.e. it is comparable to the next best amount the entrepreneur could earn doing another job.^[3] Particularly if enterprise is not included as a factor of production, it can also be viewed a return to capital for investors including the entrepreneur, equivalent to the return the capital owner could have expected (in a safe investment), plus compensation for risk.^[4] In other words, the cost of normal profit varies both within and across industries; it is commensurate with the riskiness associated with each type of investment, as per the risk-return spectrum.

Only normal profits arise in circumstances of perfect competition when long run economic equilibrium is reached; there is no incentive for firms to either enter or leave the industry.^[5]

In competitive and contestable markets

Only in the short run can a firm in a perfectly competitive market make an economic profit.

Economic profit does not occur in perfect competition in long run equilibrium; if it did, there would be an incentive for new firms to enter the industry, aided by a lack of barriers to entry until there was no longer any economic profit.^[4] As new firms enter the industry, they increase the supply of the product available in the market, and these new firms are forced to charge a lower price to entice consumers to buy the additional supply these new firms are supplying as the firms all compete for customers (See "Persistence" in the Monopoly Profit discussion).^[6][7][8][9] Incumbent firms within the industry face losing their existing customers to the new firms entering the industry, and are therefore forced to lower their prices to match the lower prices set by the new firms. New firms will continue to enter the industry until the price of the product is lowered to the point that it is the same as the average cost of producing the product, and all of the economic profit disappears.^[6][7] When this happens, economic agents outside of the industry find no advantage to forming new firms that enter into the industry, the supply of the product stops increasing, and the price charged for the product stabilizes, settling into an equilibrium.^[6][7][8]

The same is likewise true of the long run equilibria of monopolistically competitive industries and, more generally, any market which is held to be contestable. Normally, a firm that introduces a differentiated product can initially secure a temporary market power for a short while (See "Persistence" in Monopoly Profit). At this stage, the initial price the consumer must pay for the product is high, and the demand for, as well as the availability of the product in the market, will be limited. In the long run, however, when the profitability of the product is well established, and because there are few barriers to entry,^[6][7][8] the number of firms that produce this product will increase until the available supply of the product eventually becomes relatively large, the price of the product shrinks down to the level of the average cost of producing the product. When this finally occurs, all monopoly profit associated with producing and selling the product disappears, and the initial monopoly turns into a competitive industry.^[6][7][8] In the case of contestable markets, the cycle is often ended with the departure of the former "hit and run" entrants to the market, returning the industry to its previous state, just with a lower price and no economic profit for the incumbent firms.

Profit can, however, occur in competitive and contestable markets in the short run, as firms jostle for market position. Once risk is accounted for, long-lasting economic profit in a competitive market is thus viewed as the result of constant cost-cutting and performance improvement ahead of industry competitors, allowing costs to be below the market-set price.

In uncompetitive markets

A monopolist can set a price in excess of costs, making an economic profit (shaded). The above Picture shows a Monopolist (only 1 Firm in the Industry/Market) that obtains a (Monopoly) Economic Profit. An Oligopoly usually has "Economic Profit" also, but usually faces an Industry/Market with more than just 1 Firm (they must share available Demand at the Market Price).

Economic profit is, however, much more prevalent in uncompetitive markets such as in a perfect monopoly or oligopoly situation. In these scenarios, individual firms have some element of market power: Though monopolists are constrained by consumer demand, they are not price takers, but instead either price-setters or quantity setters. This allows the firm to set a price which is higher than that which would be found in a similar but more competitive industry, allowing them economic profit in both the long and short run.^[6][7]

The existence of economic profits depends on the prevalence of barriers to entry: these stop other firms from entering into the industry and sapping away profits,^[9] like they would in a more competitive market. In cases where barriers are present, but more than one firm, firms can collude to limit production, thereby restricting supply in order to ensure the price of the product remains high enough to ensure all of the firms in the industry achieve an economic profit.^[6][9][10]

However, some economists, for instance Steve Keen, a professor at the University of Western Sydney, argue that even an infinitesimal amount of market power can allow a firm to produce a profit and that the absence of economic profit in an industry, or even merely that some production occurs at a loss, in and of itself constitutes a barrier to entry.

In a single-goods case, a positive economic profit happens when the firm's average cost is less than the price of the product or service at the profit-maximizing output. The economic profit is equal to the quantity of output multiplied by the difference between the average cost and the price.

Government intervention

Often, governments will try to intervene in uncompetitive markets to make them more competitive. Antitrust (US) or competition (elsewhere) laws were created to prevent powerful firms from using their economic power to artificially create the barriers to entry they need to protect their economic profits.^[7][8][9] This includes the use of predatory pricing toward smaller competitors.^[6][9][10] For example, in the United States, Microsoft Corporation was initially convicted of breaking Anti-Trust Law and engaging in anti-competitive behavior in order to form one such barrier in United States v. Microsoft; after a successful appeal on technical grounds, Microsoft agreed to a settlement with the Department of Justice in which they were faced with stringent oversight procedures and explicit requirements^[11] designed to prevent this predatory behaviour. With lower barriers, new firms can enter the market again, making the long run equilibrium much more like that of a competitive industry, with no economic profit for firms.

In a regulated industry, the government examines firms' marginal cost structure and allows them to charge a price that is no greater than this marginal cost. This does not necessarily ensure zero Economic profit for the firm, but eliminates a "Pure Monopoly" Profit.

If a government feels it is impractical to have a competitive market – such as in the case of a natural monopoly – it will sometimes try to regulate the existing uncompetitive market by controlling the price firms charge for their product.^[7][8] For example, the old AT&T (regulated) monopoly, which existed before the courts ordered its breakup, had to get government approval to raise its prices. The government examined the monopoly's costs, and determined whether or not the monopoly should be able raise its price and if the government felt that the cost did not justify a higher price, it rejected the monopoly's application for a higher price. Though a regulated firm will not have an economic profit as large as it would in an unregulated situation, it can still make profits well above a competitive firm in a truly competitive market.^[8]

Example: Nash equilibrium

Equilibrium quantities as a solution to two reaction functions in Cournot duopoly. Firm 1's reaction function q1=R1(q2) gives its optimal output q1 to a given output q2 of firm 2. Likewise, firm 2's reaction function q2=R2(q1). The Cournot-Nash equilibrium occurs where the two reaction functions intersect and both firms are choosing the optimal output given the output of the other firm.

The Nash equilibrium is widely used in economics as the main alternative to competitive equilibrium. It is used whenever there is a strategic element to the behavior of agents and the "price taking" assumption of competitive equilibrium is inappropriate. The first use of the Nash equilibrium was in the Cournot duopoly as developed by Antoine Augustin Cournot in his 1838 book.^[12] Both firms produce a homogenous product: given the total amount supplied by the two firms, the (single) industry price is determined using the demand curve. This determines the revenues of each firm (the industry price times the quantity supplied by the firm). The profit of each firm is then this revenue minus the cost of producing the output. Clearly, there is a strategic interdependence between the two firms. If one firm varies its output, this will in turn affect the market price and so the revenue and profits of the other firm. We can define the payoff function which gives the profit of each firm as a function of the two outputs chosen by the firms. Cournot assumed that each firm chooses its own output to maximize its profits given the output of the other firm. The Nash equilibrium occurs when both firms are producing the outputs which maximize their own profit given the output of the other firm.

In terms of the equilibrium properties, we can see that P2 is satisfied: in a Nash equilibrium, neither firm has an incentive to deviate from the Nash equilibrium given the output of the other firm. P1 is satisfied since the payoff function ensures that the market price is consistent with the outputs supplied and that each firms profits equal revenue minus cost at this output.

Is the equilibrium stable as required by P3? Cournot himself argued that it was stable using the stability concept implied by best response dynamics. The reaction function for each firm gives the output which maximizes profits (best response) in terms of output for a firm in terms of a given output of the other firm. In the standard Cournot model this is downward sloping: if the other firm produces a higher output, your best response involves producing less. Best response dynamics involves firms starting from some arbitrary position and then adjusting output to their best-response to the previous output of the other firm. So long as the reaction functions have a slope of less than -1, this will converge to the Nash equilibrium. However, this stability story is open to much criticism. As Dixon argues: "The crucial weakness is that, at each step, the firms behave myopically: they choose their output to maximize their current profits given the output of the other firm, but ignore the fact that the process specifies that the other firm will adjust its output...".^[13] There are other concepts of stability that have been put forward for the Nash equilibrium, evolutionary stability for example.

Normative evaluation

Most economists e.g., Paul Samuelson^{[14]:Ch.3,p.52} caution against attaching a normative meaning (value judgement) to the equilibrium price. For example, food markets may be in equilibrium at the same time that people are starving (because they cannot afford to pay the high equilibrium price). Indeed, this occurred during the Great Famine in Ireland in 1845–52, where food was exported though people were starving, due to the greater profits in selling to the English – the equilibrium price of the Irish-British market for potatoes was above the price that Irish farmers could afford, and thus (among other reasons) they starved.^[15]

Interpretations

In most interpretations, classical economists such as Adam Smith maintained that the free market would tend towards economic equilibrium through the price mechanism. That is, any excess supply (market surplus or glut) would lead to price cuts, which decrease the quantity supplied (by reducing the incentive to produce and sell the product) and increase the quantity demanded (by offering consumers bargains), automatically abolishing the glut. Similarly, in an unfettered market, any excess demand (or shortage) would lead to price increases, reducing the quantity demanded (as customers are priced out of the market) and increasing in the quantity supplied (as the incentive to produce and sell a product rises). As before, the disequilibrium (here, the shortage) disappears. This automatic abolition of non-market-clearing situations distinguishes markets from central planning schemes, which often have a difficult time getting prices right and suffer from persistent shortages of goods and services.^[16]

This view came under attack from at least two viewpoints. Modern mainstream economics points to cases where equilibrium does not correspond to market clearing (but instead to unemployment), as with the efficiency wage hypothesis in labor economics. In some ways parallel is the phenomenon of credit rationing, in which banks hold interest rates low to create an excess demand for loans, so they can pick and choose whom to lend to. Further, economic equilibrium can correspond with monopoly, where the monopolistic firm maintains an artificial shortage to prop up prices and to maximize profits. Finally, Keynesian macroeconomics points to underemployment equilibrium, where a surplus of labor (i.e., cyclical unemployment) co-exists for a long time with a shortage of aggregate demand.

Solving for the competitive equilibrium price

To solve for the equilibrium price, one must either plot the supply and demand curves, or solve for their equations being equal.

An example may be:

$\begin{alignat}{2} Q_s & = 125 + 1.5 \cdot P \\ Q_d & = 189 - 2.25 \cdot P \\ \\ Q_s & = Q_d \\ \\ 124 + 1.5 \cdot P & = 189 - 2.25 \cdot P \\ (1.5 + 2.25) \cdot P & = (189 +124) \\ P & = \frac{189 - 124}{1.5 + 2.25} \\ P & = \frac{65}{3.75} \\ P & = 17.33 \\ \end{alignat}$

In the diagram, depicting simple set of supply and demand curves, the quantity demanded and supplied at price P are equal.

At any price above P supply exceeds demand, while at a price below P the quantity demanded exceeds that supplied. In other words, prices where demand and supply are out of balance are termed points of disequilibrium, creating shortages and oversupply. Changes in the conditions of demand or supply will shift the demand or supply curves. This will cause changes in the equilibrium price and quantity in the market.

Consider the following demand and supply schedule:

Price ($)	Demand	Supply
8.00	6,000	18,000
7.00	8,000	16,000
6.00	10,000	14,000
5.00	12,000	12,000
4.00	14,000	10,000
3.00	16,000	8,000
2.00	18,000	6,000
1.00	20,000	4,000

• The equilibrium price in the market is $5.00 where demand and supply are equal at 12,000 units
• If the current market price was $3.00 – there would be excess demand for 8,000 units, creating a shortage.
• If the current market price was $8.00 – there would be excess supply of 12,000 units.

When there is a shortage in the market we see that, to correct this disequilibrium, the price of the good will be increased back to a price of $5.00, thus lessening the quantity demanded and increasing the quantity supplied thus that the market is in balance.

When there is an oversupply of a good, such as when price is above $6.00, then we see that producers will decrease the price to increase the quantity demanded for the good, thus eliminating the excess and taking the market back to equilibrium.

Influences changing price

A change in equilibrium price may occur through a change in either the supply or demand schedules. For instance, starting from the above supply-demand configuration, an increased level of disposable income may produce a new demand schedule, such as the following:

Price ($)	Demand	Supply
8.00	10,000	18,000
7.00	12,000	16,000
6.00	14,000	14,000
5.00	16,000	12,000
4.00	18,000	10,000
3.00	20,000	8,000
2.00	22,000	6,000
1.00	24,000	4,000

Here we see that an increase in disposable income would increase the quantity demanded of the good by 2,000 units at each price. This increase in demand would have the effect of shifting the demand curve rightward. The result is a change in the price at which quantity supplied equals quantity demanded. In this case we see that the two now equal each other at an increased price of $6.00. Note that a decrease in disposable income would have the exact opposite effect on the market equilibrium .

We will also see similar behaviour in price when there is a change in the supply schedule, occurring through technological changes, or through changes in business costs. An increase in technological usage or know-how or a decrease in costs would have the effect of increasing the quantity supplied at each price, thus reducing the equilibrium price. On the other hand, a decrease in technology or increase in business costs will decrease the quantity supplied at each price, thus increasing equilibrium price.

The process of comparing two static equilibria to each other, as in the above example, is known as comparative statics. For example, since a rise in consumers' income leads to a higher price (and a decline in consumers' income leads to a fall in the price — in each case the two things change in the same direction), we say that the comparative static effect of consumer income on the price is positive. This is another way of saying that the total derivative of price with respect to consumer income is greater than zero.

Dynamic equilibrium

Whereas in a static equilibrium all quantities have unchanging values, in a dynamic equilibrium various quantities may all be growing at the same rate, leaving their ratios unchanging. For example, in the neoclassical growth model, the working population is growing at a rate which is exogenous (determined outside the model, by non-economic forces). In dynamic equilibrium, output and the physical capital stock also grow at that same rate, with output per worker and the capital stock per worker unchanging. Similarly, in models of inflation a dynamic equilibrium would involve the price level, the nominal money supply, nominal wage rates, and all other nominal values growing at a single common rate, while all real values are unchanging, as is the inflation rate.^[17]

The process of comparing two dynamic equilibria to each other is known as comparative dynamics. For example, in the neoclassical growth model, starting from one dynamic equilibrium based in part on one particular saving rate, a permanent increase in the saving rate leads to a new dynamic equilibrium in which there are permanently higher capital per worker and productivity per worker, but an unchanged growth rate of output; so it is said that in this model the comparative dynamic effect of the saving rate on capital per worker is positive but the comparative dynamic effect of the saving rate on the output growth rate is zero.

Disequilibrium

Disequilibrium characterises a market that is not in equilibrium.^[18] Disequilibrium can occur extremely briefly or over an extended period of time. Typically in financial markets it either never occurs or only momentarily occurs, because trading takes place continuously and the prices of financial assets can adjust instantaneously with each trade to equilibrate supply and demand. At the other extreme, many economists view labor markets as being in a state of disequilibrium—specifically one of excess supply—over extended periods of time. Goods markets are somewhere in between: prices of some goods, while sluggish in adjusting due to menu costs, long term contracts, and other impediments, do not stay at disequilibrium levels indefinitely, and many goods markets such as commodity markets are highly organised and liquid and have essentially instantaneous adjustment of their prices to equilibrium levels.

Credit markets

Disequilibrium credit rationing can occur for one of two reasons. In the presence of usury laws, if the equilibrium interest rate on loans is above the legally allowable rate, the market cannot clear and at the maximum allowable rate the quantity of credit demanded will exceed the quantity of credit supplied.

A more subtle source of credit rationing is that higher interest rates can increase the risk of default by the borrower, making the potential lender reluctant to lend at otherwise attractively high interest rates.

Labour markets

Labour markets are prone to particular sources of price rigidity because the item being transacted is people, and laws or social constraints designed to protect those people may hinder market adjustments. Such constraints include restrictions on who or how many people can be laid off and when (which can affect both the number of layoffs and the number of people hired by firms that are concerned by the restrictions), restrictions on the lowering of wages when a firm experiences a decline in the demand for its product, and long-term labor contracts that pre-specify wages.

Spillovers between markets

Disequilibrium in one market can affect demand or supply in other markets. Specifically, if an economic agent is constrained in one market, his supply or demand in another market may be changed from its unconstrained form, termed the notional demand, into a modified form known as effective demand. If this occurs systematically for a large number of market participants, market outcomes in the latter market for prices and quantities transacted (themselves either equilibrium or disequilibrium outcomes) will be affected.

Examples include:

• If the supply of mortgage credit to potential homebuyers is rationed, this will decrease the demand for newly built houses.
• If labourers cannot supply all the labor they wish to, they will have constrained income and their demand in the goods market will be lower.
• If employers cannot hire all the labor they wish to, they cannot produce as much output as they wish to, and supply in the market for their good will be diminished.

See also

• Competitive equilibrium
• General equilibrium theory
• Partial equilibrium
• Nash equilibrium
• Labor theory of value
• Price
• Exchange value
• Supply and demand
• Microeconomics
• Real prices and ideal prices
• Prices of production
• Law of value

References

1. Varian, Hal R. (1992). Microeconomic Analysis (Third ed.). New York: Norton. ISBN 0-393-95735-7.
2. Dixon, H. (1990). "Equilibrium and Explanation". In Creedy. The Foundations of Economic Thought. Blackwells. pp. 356–394. ISBN 0-631-15642-9. (reprinted in Surfing Economics).
3. Carbaugh, 2006. p.84.
4. Lipsey, 1975. p. 217.
5. Lipsey, 1975. pp. 285–259.
6. Chiller, 1991.
7. Mansfield, 1979.
8. LeRoy Miller, 1982.
9. Tirole, 1988.
10. Black, 2003.
11. "United States of America, Plaintiff, v. Microsoft Corporation, Defendant", Final Judgement, Civil Action No. 98-1232, November 12, 2002.
12. Augustin Cournot (1838), Theorie mathematique de la richesse sociale and of recherches sur les principles mathematiques de la theorie des richesses, Paris
13. Dixon (1990), page 369.
14. Paul A. Samuelson (1947; Expanded ed. 1983), Foundations of Economic Analysis, Harvard University Press. ISBN 0-674-31301-1
15. See citations at Great Famine (Ireland): Food exports to England, including Cecil Woodham-Smith The Great Hunger; Ireland 1845–1849, and Christine Kinealy, 'Irish Famine: This Great Calamity and A Death-Dealing Famine'
16. Smith, Adam (1776), Wealth of Nations, Penn State Electronic Classics edition, republished 2005, Chapter 7: p.51-58
17. Turnovsky, Stephen J. (2000). Methods of Macroeconomic Dynamics. MIT Press. ISBN 0-262-20123-2.
18. Sullivan, Arthur; Steven M. Sheffrin (2003). Economics: Principles in action. Upper Saddle River, New Jersey 07458: Pearson Prentice Hall. p. 550. ISBN 0-13-063085-3.

External links

• Equilibrium and Explanation, chapter 2 of Surfing Economics by Huw Dixon