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Why does a shift in perceived demand cause a shift in marginal revenue?

The combinations of price and quantity at each point on a firm’s perceived demand curve are used to calculate total revenue for each combination of price and quantity. This information on total revenue is then used to calculate marginal revenue, which is the change in total revenue divided by the change in quantity. A change in perceived demand will change total revenue at every quantity of output and in turn, the change in total revenue will shift marginal revenue at each quantity of output. Thus, when entry occurs in a monopolistically competitive industry, the perceived demand curve for each firm will shift to the left, because a smaller quantity will be demanded at any given price. Another way of interpreting this shift in demand is to notice that, for each quantity sold, a lower price will be charged. Consequently, the marginal revenue will be lower for each quantity sold—and the marginal revenue curve will shift to the left as well. Conversely, exit causes the perceived demand curve for a monopolistically competitive firm to shift to the right and the corresponding marginal revenue curve to shift right, too.

A monopolistically competitive industry does not display productive and allocative efficiency in either the short run, when firms are making economic profits and losses, nor in the long run, when firms are earning zero profits.

The benefits of variety and product differentiation

Even though monopolistic competition does not provide productive efficiency or allocative efficiency, it does have benefits of its own. Product differentiation is based on variety and innovation. Many people would prefer to live in an economy with many kinds of clothes, foods, and car styles; not in a world of perfect competition where everyone will always wear blue jeans and white shirts, eat only spaghetti with plain red sauce, and drive an identical model of car. Many people would prefer to live in an economy where firms are struggling to figure out ways of attracting customers by methods like friendlier service, free delivery, guarantees of quality, variations on existing products, and a better shopping experience.

Economists have struggled, with only partial success, to address the question of whether a market-oriented economy produces the optimal amount of variety. Critics of market-oriented economies argue that society does not really need dozens of different athletic shoes or breakfast cereals or automobiles. They argue that much of the cost of creating such a high degree of product differentiation, and then of advertising and marketing this differentiation, is socially wasteful—that is, most people would be just as happy with a smaller range of differentiated products produced and sold at a lower price. Defenders of a market-oriented economy respond that if people do not want to buy differentiated products or highly advertised brand names, no one is forcing them to do so. Moreover, they argue that consumers benefit substantially when firms seek short-term profits by providing differentiated products. This controversy may never be fully resolved, in part because deciding on the optimal amount of variety is very difficult, and in part because the two sides often place different values on what variety means for consumers. Read the following Clear It Up feature for a discussion on the role that advertising plays in monopolistic competition.

How does advertising impact monopolistic competition?

The U.S. economy spent about $180.12 billion on advertising in 2014, according to eMarketer.com. Roughly one third of this was television advertising, and another third was divided roughly equally between Internet, newspapers, and radio. The remaining third was divided up between direct mail, magazines, telephone directory yellow pages, and billboards. Mobile devices are increasing the opportunities for advertisers.

Advertising is all about explaining to people, or making people believe, that the products of one firm are differentiated from the products of another firm. In the framework of monopolistic competition, there are two ways to conceive of how advertising works: either advertising causes a firm’s perceived demand curve to become more inelastic (that is, it causes the perceived demand curve to become steeper); or advertising causes demand for the firm’s product to increase (that is, it causes the firm’s perceived demand curve to shift to the right). In either case, a successful advertising campaign may allow a firm to sell either a greater quantity or to charge a higher price, or both, and thus increase its profits.

However, economists and business owners have also long suspected that much of the advertising may only offset other advertising. Economist A. C. Pigou wrote the following back in 1920 in his book, The Economics of Welfare :

It may happen that expenditures on advertisement made by competing monopolists [that is, what we now call monopolistic competitors] will simply neutralise one another, and leave the industrial position exactly as it would have been if neither had expended anything. For, clearly, if each of two rivals makes equal efforts to attract the favour of the public away from the other, the total result is the same as it would have been if neither had made any effort at all.

Key concepts and summary

Monopolistic competition refers to a market where many firms sell differentiated products. Differentiated products can arise from characteristics of the good or service, location from which the product is sold, intangible aspects of the product, and perceptions of the product.

The perceived demand curve for a monopolistically competitive firm is downward-sloping, which shows that it is a price maker and chooses a combination of price and quantity. However, the perceived demand curve for a monopolistic competitor is more elastic than the perceived demand curve for a monopolist, because the monopolistic competitor has direct competition, unlike the pure monopolist. A profit-maximizing monopolistic competitor will seek out the quantity where marginal revenue is equal to marginal cost. The monopolistic competitor will produce that level of output and charge the price that is indicated by the firm’s demand curve.

If the firms in a monopolistically competitive industry are earning economic profits, the industry will attract entry until profits are driven down to zero in the long run. If the firms in a monopolistically competitive industry are suffering economic losses, then the industry will experience exit of firms until economic profits are driven up to zero in the long run.

A monopolistically competitive firm is not productively efficient because it does not produce at the minimum of its average cost curve. A monopolistically competitive firm is not allocatively efficient because it does not produce where P = MC, but instead produces where P>MC. Thus, a monopolistically competitive firm will tend to produce a lower quantity at a higher cost and to charge a higher price than a perfectly competitive firm.

Monopolistically competitive industries do offer benefits to consumers in the form of greater variety and incentives for improved products and services. There is some controversy over whether a market-oriented economy generates too much variety.


Andrea’s Day Spa began to offer a relaxing aromatherapy treatment. The firm asks you how much to charge to maximize profits. The demand curve for the treatments is given by the first two columns in [link] ; its total costs are given in the third column. For each level of output, calculate total revenue, marginal revenue, average cost, and marginal cost. What is the profit-maximizing level of output for the treatments and how much will the firm earn in profits?

Price Quantity TC
$25.00 0 $130
$24.00 10 $275
$23.00 20 $435
$22.50 30 $610
$22.00 40 $800
$21.60 50 $1,005
$21.20 60 $1,225
Got questions? Get instant answers now!


Kantar Media. “Our Insights: Infographic—U.S. Advertising Year End Trends Report 2012.” Accessed October 17, 2013. http://kantarmedia.us/insight-center/reports/infographic-us-advertising-year-end-trends-report-2012.

Statistica.com. 2015. “Number of Restaurants in the United States from 2011 to 2014.” Accessed March 27, 2015. http://www.statista.com/statistics/244616/number-of-qsr-fsr-chain-independent-restaurants-in-the-us/.

Questions & Answers

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it is a Price at which there is no tendency for both the quantity demanded and quantity supplied to change.
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joint demand?
is when two commodities relate together
it refers to the demand for two commodities that are jountly consumed or used together
It is when commodities are used together
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The Four Asian Tigers, Four Asian Dragons or Four Little Dragons, are the economies of Hong Kong, Singapore, South Korea and Taiwan, which underwent rapid industrialization and maintained exceptionally high growth rates between the early 1960s and 1990s.
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gross domestic product
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Inflation is defined as the rise in price of a commodity.
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It is defined as the rise in price of a commodity.
the persistent rise in the prices of goods and services. or commodities.
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what's GDP?
gross domestic product
GDP stands for Gross Domestic Product
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Maxima s below equilibrium. Whilst minima s above. Equilibrium
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is the willingness and the ability of a consumer to purchase goods at a given price and at a particular point in time.
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why is the demand curve downwards sloppy?
3 Reasons.. 1... diminishing marginal utility 2... substitution effect 3...income effect
Because of the negative or inverse relationship between price and quantity demanded
what is the law of diminishing returns states?
The law states that all other things being equall as much of variable factor(labour) is employed on fixed factor(land) the marginal product rises..attain a maximum and begins to fall.
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Monetary policy is an attempt to influence the economy by opera ting in such monetary variables
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is disutility? is rightly writing?
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Yes please Disutility
what is macro economics?
the branch of economics concerned with large-scale or general economic factors, such as interest rates and national productivity.
in other words it is the study of the economic as a whole
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Economic growth is the process whereby the real per capita income of an economy increases over a long period of time.
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Economics is defined by Lionel Robbins as a social science which studies human behaviour as a relationship between ends and scarce means which have alternative uses
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Importance of economic
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Helps in decision making
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if an individual is faced with unlimited wants.
it also helps an individual in arranging their wants in order of their importance.
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it's use for arranging wants in order of their importance.
in other words when an individual is faced with unlimited wants,scale of preference would help the individual to select the most important wants.
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Tourism is travel for pleasure or business
It is the commercial organization and operation of holidays and visits to places of interest.
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A price taker is a person or a company who have no control to dictate a prices of a goods or services
Someone who sets price
In the trading world, a price taker is a trader who does not affect the price of the stock if he or she buys or sells shares.
A price taker refers to a firm or an individual who sets the price of his good and services based on an external factor. In other words he cannot choose and set a price by himself. An example is a firm operating in perfect competition where prices are set through the price mechanism.
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The higher the satisfaction derived from a particular commodity,the lower the demand for it but that law doesn't match in some instances.
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imperfect competitive market involves large number of sellers and buyers price makers selling cost product differentiation free entry and exit of a firms

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Source:  OpenStax, Principles of economics. OpenStax CNX. Sep 19, 2014 Download for free at http://legacy.cnx.org/content/col11613/1.11
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