Barriers to Entry
What is Barriers to Entry?
Barriers to entry are obstacles that make it difficult for new firms to enter a market and compete with existing firms.
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.
Barriers to Entry: a worked example
An incumbent bottler and a would be entrant use identical technology: $9,000 of fixed cost for a bottling line and $5 of variable cost per case. The incumbent already moves 10,000 cases, so its average fixed cost is $9,000 / 10,000 = $0.90 and its ATC is $5 + $0.90 = $5.90. A newcomer starting at 1,000 cases carries average fixed cost of $9,000 / 1,000 = $9.00 and ATC of $5 + $9.00 = $14.00. At a market price of $7 the incumbent earns $7.00 - $5.90 = $1.10 per case, or $11,000, while the entrant loses $14.00 - $7.00 = $7.00 per case, or $7,000. To break even the entrant would have to reach $9,000 / ($7 - $5) = 4,500 cases and absorb losses on every case until it got there. That cost gap, not any rule forbidding entry, is the barrier.
The mistake students make with barriers to entry
On free response questions students explain a monopolist's lasting profit by pointing at the downward sloping demand curve. That slope explains why the firm can set price at a moment in time, but it says nothing about why rivals never show up to compete the profit away. Barriers to entry do that job. A monopolistically competitive shop also faces downward sloping demand, yet entry is easy and its economic profit disappears in the long run. When a prompt asks why long run profit persists, name the specific barrier, a patent, a license, control of an input or scale economies, and say plainly that it blocks entry.
Barriers to Entry questions
What are the main types of barriers to entry?
Four types carry most AP Microeconomics questions: control of a scarce resource, such as the only quarry in a region; government created barriers including patents, copyrights and operating licenses; large sunk startup costs a firm cannot recover if it exits; and economies of scale, where an incumbent's average total cost keeps falling across the whole range of market demand. Strong brand loyalty and exclusive supply contracts work as softer versions of the same idea.
Why do barriers to entry lead to long run economic profit?
Entry is the mechanism that normally erases profit. In a market anyone can join, positive economic profit attracts new firms, supply grows, price falls and profit is squeezed toward zero. Barriers switch that mechanism off, so an incumbent charging above average total cost can keep doing it indefinitely. The size of the profit depends on demand and costs, but the durability of it depends entirely on how solid the barrier turns out to be.
Are there barriers to entry in monopolistic competition?
Monopolistic competition is defined by easy entry and exit, so meaningful barriers are absent. Firms differentiate their products and each faces a downward sloping demand curve, yet any short run profit invites new sellers with close substitutes until each firm's demand shifts left far enough that price equals average total cost. That is precisely why the long run outcome there is zero economic profit rather than the lasting profit a protected monopoly enjoys.
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