Introduction to Imperfectly Competitive Markets
| English | Chinese | Pinyin |
|---|---|---|
| market power | 市场势力 | shì chǎng shì lì |
| imperfectly competitive market | 不完全竞争市场 | bù wán quán jìng zhēng shì chǎng |
| price taker | 价格接受者 | jià gé jiē shòu zhě |
| downward-sloping demand curve | 向下倾斜的需求曲线 | xiàng xià qīng xié de xū qiú qū xiàn |
| monopoly | 垄断 | lǒng duàn |
| monopolistic competition | 垄断竞争 | lǒng duàn jìng zhēng |
| oligopoly | 寡头垄断 | guǎ tóu lǒng duàn |
| monopsony | 买方垄断 | mǎi fāng lǒng duàn |
| barriers to entry | 进入壁垒 | jìn rù bì lěi |
| economic profit | 经济利润 | jīng jì lì rùn |
Most markets aren't "perfect"
- Perfect competition is a useful benchmark — but almost no real market matches it.
- Your phone network, favourite cafe, and local cinema all set their own prices.
- Any firm that can nudge its price has some market power 市场势力.
- The markets where this happens are called imperfectly competitive markets 不完全竞争市场.
Market power means a downward demand curve
- A price taker 价格接受者 faces a flat demand curve — it sells all it wants at the market price.
- An imperfect competitor faces a downward-sloping demand curve 向下倾斜的需求曲线 — to sell more, it must lower its price.
- That is exactly what market power is: the ability to set price above marginal cost.

A firm with market power faces a demand curve that is:
To sell more it must lower its price — a downward-sloping demand curve.
A price taker can raise its price above the market price and still sell everything.
A price taker must accept the market price; charging more loses all its buyers.
Four imperfect structures
- Monopoly 垄断: one firm, no close substitutes.
- Oligopoly 寡头垄断: a few large firms that watch each other.
- Monopolistic competition 垄断竞争: many firms selling slightly different products.
- Monopsony 买方垄断: one big buyer — the mirror image of monopoly.
Which market structure?
Structures differ by how many firms there are and how similar their products are — from perfect competition to monopoly.
Match each structure to its defining feature.
They differ by number of firms, product similarity, and (for monopsony) being a buyer.
Barriers to entry
- What lets these firms keep economic profit 经济利润 even in the long run is barriers to entry 进入壁垒.
- A barrier is anything that stops new firms coming in to compete the profit away.
- Common barriers: large start-up costs, control of a key resource, patents, and government licences.
Anything that stops new firms from entering a market is a ______ to entry.
Barriers to entry protect economic profit in the long run.
Select all that are barriers to entry.
Patents, key resources and high start-up costs block entry; many competitors is the opposite.
An imperfectly competitive firm has market power — a downward-sloping demand curve and price above marginal cost. The four structures are monopoly, oligopoly, monopolistic competition, and monopsony. Barriers to entry protect their long-run profit.