Impact of Market Structure on Revenue Functions

Every firm makes money by selling something, but exactly how that money grows as sales increase depends heavily on the kind of market the firm operates in. This relationship between quantity sold and revenue earned is called a revenue function, and its shape changes completely depending on market structure. A vegetable vendor in a local mandi earns revenue very differently from a telecom company like Reliance Jio or Bharti Airtel. Understanding why market structure reshapes revenue functions helps explain how firms set prices, decide how much to produce, and ultimately maximise profit.

What a revenue function actually measures 🔗

Before comparing market structures, it helps to be clear on three related revenue concepts that together make up a firm’s revenue function.

Total revenue (TR) is simply price multiplied by quantity sold: TR = P × Q. Average revenue (AR) is revenue earned per unit, calculated as TR divided by Q, which mathematically always equals price (AR = P). Marginal revenue (MR) is the extra revenue earned from selling one additional unit, or the change in total revenue divided by the change in quantity.

These three curves behave very differently depending on whether a firm can set its own price or must accept the price the market gives it. That single distinction, whether a firm is a price taker or a price maker, is what separates perfect competition from every other market structure.

Perfect competition: the price taker’s flat revenue curve 🔗

In a perfectly competitive market, there are many small firms selling an identical product, and no single seller is large enough to influence the market price. Each firm simply accepts the price determined by overall market demand and supply, which is why economists describe such a firm as a price taker facing a horizontal demand curve at the market price. If the firm tries to charge even slightly more, buyers simply move to a competitor selling an identical product.

This has a direct mathematical consequence for the revenue function. Since price stays constant no matter how much the firm sells, average revenue and marginal revenue both equal that fixed price. This gives the well-known equality AR = MR = P, and all three appear as a single flat, horizontal line on a graph.

A simple revenue schedule 🔗

Suppose the market price of wheat is fixed at ₹25 per kg for an individual farmer who cannot influence this price.

Notice that total revenue keeps rising in a straight line, while AR and MR remain unchanged. This flat revenue structure is why perfectly competitive firms focus purely on producing efficiently rather than on pricing strategy; price is simply not a decision variable available to them.

Imperfect competition: when firms become price makers 🔗

Once a market moves away from perfect competition, whether into monopoly, monopolistic competition, or oligopoly, firms gain some control over price. This happens because products are no longer perfectly identical, or because there are few enough sellers that each one’s output decisions actually affect the market price. The firm now faces a downward-sloping demand curve rather than a flat one, meaning it must lower its price to sell additional units.

Why marginal revenue falls faster than average revenue 🔗

This is where the revenue function of an imperfectly competitive firm becomes genuinely more complex than that of a perfectly competitive one. Because average revenue (price) is downward sloping, marginal revenue is not just lower than price, it actually falls at roughly twice the rate. This happens because when a firm cuts price to sell one more unit, it does not just earn the lower price on that new unit, it also earns less on every unit it was already selling at the higher price. For a straight-line demand curve, marginal revenue shares the same starting price intercept as demand but falls twice as steeply, so the horizontal point where MR hits zero occurs at exactly half the output level where demand itself would reach a zero price.

Consider a monopolist facing the linear demand relationship P = 200 − 4Q. Using the standard shortcut, marginal revenue works out to MR = 200 − 8Q, precisely double the slope of the demand curve.

Beyond a certain output level, marginal revenue can even turn negative, meaning that selling more units actually reduces total revenue because the price cut required drags down earnings on all the previously sold units too. This is why a profit-maximising monopolist or any firm with pricing power always restricts output well below what a perfectly competitive market would produce, choosing the quantity where marginal revenue equals marginal cost rather than pushing output indefinitely.

Oligopoly: revenue dynamics under strategic uncertainty 🔗

Oligopoly adds a further layer of complexity because a handful of large firms dominate the market and are keenly aware that their pricing decisions directly affect competitors, and vice versa. This mutual interdependence means an oligopolist’s revenue function cannot be drawn with the same confidence as a monopolist’s, since it depends on how rivals are expected to react.

The kinked demand curve and price rigidity 🔗

One influential explanation for oligopoly pricing behaviour is the kinked demand curve model. It assumes that if a firm raises its price above the prevailing market level, rivals will not follow, so the firm loses a large chunk of sales and its demand curve is relatively elastic. But if the firm cuts its price, rivals match the cut to avoid losing customers, so the firm gains very little additional market share, making demand relatively inelastic below the current price. This asymmetry produces a demand curve with a visible kink at the existing market price, and correspondingly, the marginal revenue curve becomes discontinuous, with a vertical gap directly beneath the kink.

This gap matters a great deal for the revenue function because it means marginal cost can shift up or down within a certain range without changing the profit-maximising price or output at all. The discontinuity in marginal revenue helps explain why oligopoly prices tend to stay unusually stable even when costs fluctuate, a pattern often called price rigidity.

Market share and non-price competition 🔗

Because direct price competition can be risky and mutually damaging in an oligopoly, revenue growth often comes from non-price strategies instead: advertising, brand loyalty, product bundling, or after-sales service. India’s telecom and aviation sectors illustrate this well. India’s domestic aviation market is dominated by just two large groups controlling roughly 91 percent of passenger traffic, a textbook example of an oligopoly where firms watch each other’s pricing and capacity decisions closely rather than competing purely on ticket prices. Regulatory frameworks recognise this risk too. Government assessments of Indian markets note that concentrated industries with only a few dominant firms require close monitoring to ensure that pricing and output decisions genuinely benefit consumers rather than reflect coordinated behaviour. This regulatory attention is precisely because an oligopolist’s revenue function is shaped as much by rivals’ expected reactions as by consumer demand itself.

Comparing revenue functions across structures 🔗

What ties all three structures together is the same underlying logic: the more control a firm has over price, the more its marginal revenue diverges from its average revenue, and the more carefully it must think about output rather than simply producing as much as possible. Perfect competition rewards efficiency alone, monopoly rewards restrained output to protect price, and oligopoly rewards careful strategic anticipation of rivals.

This is also why revenue functions matter well beyond the textbook. Regulators use these same models to judge whether a dominant firm or a small cartel of firms is exploiting pricing power unfairly, and businesses use them to decide whether competing on price or competing on differentiation makes more commercial sense in their specific market.

What do you think? If you were advising a new entrant into an oligopolistic industry like Indian aviation or telecom, would you recommend competing primarily on price, or focusing on non-price strategies instead? And can you think of an Indian market that has moved from something closer to monopolistic competition toward an oligopoly in recent years, and what that shift might mean for its revenue functions?

References

1. https://socialsci.libretexts.org/Bookshelves/Economics/Introductory_Comprehensive_Economics/Economics_(Boundless)/10:_Competitive_Markets/10.01:_Perfect_Competition
2. https://openstax.org/books/principles-economics-3e/pages/9-2-how-a-profit-maximizing-monopoly-chooses-output-and-price
3. https://www.economicshelp.org/blog/glossary/kinked-demand-curve/
4. https://www.pearson.com/channels/microeconomics/study-guides/oligopoly-kinked-demand-curve-price-leadership-and
5. https://www.business-standard.com/industry/news/what-is-an-oligopoly-which-indian-sectors-have-few-dominant-players-126082400372_1.html
6. https://www.cci.gov.in/images/publications_competition_assesment/en/competition-assessment-toolkit1652242714.pdf