Barriers to Entry vs Natural Monopoly
Barriers to Entry and Natural Monopoly are two Market Structures concepts in AP Economics that students often mix up. Barriers to entry are obstacles that make it difficult for new firms to enter a market and compete with existing firms. A natural monopoly occurs when a single firm can produce the entire market output at a lower average total cost than multiple firms could. Here is how they compare side by side.
These include legal restrictions like patents, high startup costs, control of essential resources, and economies of scale. Barriers allow existing firms to maintain market power and earn long-run economic profits.
This typically happens in industries with very high fixed costs and low marginal costs, such as utilities, where economies of scale are so large that one firm is more efficient than many. Government regulation is often used to prevent abuse of market power.
Barriers to Entry vs Natural Monopoly: The Category and Its Cost-Driven Case
| Barriers to Entry | Natural Monopoly | |
|---|---|---|
| Type of thing | A category of obstacles that keep new firms out | One industry-level cost condition that produces a single seller |
| Where the obstacle comes from | Law, resource control, brand investment, scale or strategy | Average total cost that keeps falling across the whole range of market demand |
| Is a second firm technically possible | Often yes, but it is blocked from trying | Yes, and it raises the industry's cost of the same output |
| Test to apply | Ask what would stop a new firm from entering | Ask whether one firm serves the market at lower average cost than two |
| Who bears the cost of the obstacle | Buyers, who lose output that a capable rival would have supplied | No one, because duplicate capacity would be the wasteful option |
| Effect of removing it | Entry, more output and a lower price | Duplicated fixed capital and a higher cost per unit |
| Standard exam treatment | Listed as a characteristic when you classify a market structure | Drawn with ATC still falling where it meets demand, plus a regulated price |
In a natural monopoly the barrier is arithmetic, not a rule
The obstacle in a natural monopoly is the cost function itself, and the arithmetic makes it visible. Suppose a regional water network costs 240 per period in fixed capital plus 2 per unit delivered, so total cost equals 240 plus 2 times quantity. Average total cost then falls at every output: 8 at 40 units, 5 at 80 units, 4 at 120 units, 3 at 240 units. Let market demand sit at 120 units. One firm serves that market for 240 plus 240, a total cost of 480, or 4 per unit. Split the same 120 units evenly between two firms and each pays its own 240 of fixed capital, so each spends 240 plus 120, or 360, and the industry now burns 720 to deliver the identical output. Entry raised the cost of serving the market by 240, exactly one duplicated network. No patent, no license and no hostile incumbent appears anywhere in that calculation. Every other member of the barriers category works the opposite way: a rival kept out by an exclusive license or a patented process could have produced just as cheaply as the incumbent, so blocking it costs buyers output they would otherwise have had. Here the rival genuinely can enter, and the market is worse off if it does.
Lowering a legal barrier cuts the price; forcing entry here raises the cost
Because the two obstacles have opposite origins, the sensible policy for each points in the opposite direction. When a rule blocks entry, weakening the rule invites competitors whose costs match the incumbent's, and the price falls toward average cost. When falling average cost blocks entry, mandating a second firm duplicates the 240 of fixed capital from the water example and lifts industry average cost from 4 to 6 per unit, so competition makes the good more expensive to produce rather than cheaper. Regulators therefore leave one firm standing and control what it charges. Set price at the marginal cost of 2 and revenue on 120 units is 240 against total cost of 480, a loss of 240 that exactly equals the fixed capital, which is why marginal-cost pricing of a falling-cost firm needs a subsidy to survive. Set price at average cost of 4 instead and revenue is 480, equal to total cost, so the firm covers everything and earns zero economic profit while price still sits above marginal cost. Work that regulated case at /calculate/rate-of-return-regulation. The trap on a free-response answer is recommending that the firm be broken up when the diagram shows ATC still falling where it meets demand, because that picture is telling you a second firm would cost more.
Frequently asked questions
Is a natural monopoly a type of barrier to entry?
A natural monopoly is not itself a barrier; the barrier is the cost structure that creates it. When one firm's average total cost keeps falling across the whole range of market demand, an entrant serving part of that demand carries its own fixed capital and ends up with higher unit costs than the incumbent, so entering is unprofitable without anyone blocking it. Economists file that cost advantage alongside patents and licenses because the effect on the number of firms is the same, but the mechanism is arithmetic rather than legal or strategic.
Can a natural monopoly exist with no legal protection at all?
Yes, and the version the exam tests usually has none. Falling average total cost over the relevant range is enough by itself, because a would-be entrant can work out that splitting the market leaves both firms with higher unit costs than the incumbent had alone. Legal protection often gets layered on top in practice, normally paired with price regulation, but the cost condition does not need it.
Which barriers to entry are not natural monopolies?
Patents, exclusive licenses, control of a scarce input, large sunk advertising outlays and deterrent pricing all restrict entry with no falling-cost story behind them. In each of those cases a rival that got past the obstacle could produce at the same unit cost as the incumbent or lower, so competition would push the industry's costs down instead of duplicating them. That difference decides the policy: remove the obstacle in those cases, regulate the single firm in the natural-monopoly case.
Live Monopoly graph. Drag the curves, or open the full version.
Related comparisons
Get AP Econ exam tips in your inbox
Occasional emails with study tips, new interactive graphs, and exam-season reminders. Free, no spam.
No spam. Unsubscribe anytime. Read our privacy policy.
Keep track of what you have studied
A free EconLearn account adds progress tracking, your quiz history, and achievements. Studying here is free either way, and there is nothing to pay for as a student.
Create a free accountAlready have one? Sign in
Last updated