Market Equilibrium and Surplus · 市场均衡与剩余
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| equilibrium/ˌiːkwɪˈlɪbrɪəm/ | 均衡 | jūn héng |
| equilibrium price/ˌiːkwɪˈlɪbrɪəm praɪs/ | 均衡价格 | jūn héng jià gé |
| equilibrium quantity/ˌiːkwɪˈlɪbrɪəm ˈkwɒntɪti/ | 均衡数量 | jūn héng shù liàng |
| producer surplus/prəˈdjuːsə ˈsɜːpləs/ | 生产者剩余 | shēng chǎn zhě shèng yú |
| consumer surplus/kənˈsuːmə ˈsɜːpləs/ | 消费者剩余 | xiāo fèi zhě shèng yú |
| total surplus/ˈtəʊtl ˈsɜːpləs/ | 总剩余 | zǒng shèng yú |
| allocative efficiency/ˈæləkətɪv ɪˈfɪʃənsi/ | 配置效率 | pèi zhì xiào lǜ |
| marginal benefit/ˈmɑːdʒɪnl ˈbenɪfɪt/ | 边际收益 | biān jì shōu yì |
The price that clears the market
- Buyers want to pay as little as possible; sellers want to charge as much as possible.
- Yet markets settle on one price where their plans match exactly.
- At that price, the amount buyers want equals the amount sellers offer.
- It is the equilibrium 均衡 — and it comes with hidden gains for both sides.
让市场出清的价格
- 买家想尽量少付;卖家想尽量多收。
- 可市场最终会停在一个价格上,让双方的计划恰好吻合。
- 在那个价格下,买家想要的量等于卖家提供的量。
- 这就是均衡(equilibrium)——它还给双方带来隐藏的收益。
Where demand meets supply
- Equilibrium is where the demand and supply curves cross.
- The equilibrium price 均衡价格 is where quantity demanded equals quantity supplied.
- The equilibrium quantity 均衡数量 is the amount actually bought and sold.
需求与供给相遇之处
- 均衡是需求曲线与供给曲线相交的地方。
- 均衡价格(equilibrium price)是需求量等于供给量的价格。
- 均衡数量(equilibrium quantity)是实际买卖的量。
Find the equilibrium · 找到均衡
Equilibrium sits where supply crosses demand. Above it there is a surplus; below it a shortage — the price is pushed back to where the two curves meet. · 均衡就在供给与需求相交处。它上方有过剩,下方有短缺——价格会被推回两条曲线相遇的地方。
At market equilibrium: · 在市场均衡处:
Equilibrium is exactly where the two quantities match and the curves cross. · 均衡正是两个数量相等、曲线相交之处。
Consumer and producer surplus
- Consumer surplus 消费者剩余 is the area below the demand curve and above the price — buyers paying less than they were willing to.
- Producer surplus 生产者剩余 is the area above the supply curve and below the price — sellers getting more than they would accept.
- Both are triangles, so each area is $\tfrac{1}{2} \times \text{base} \times \text{height}$.
- Total surplus 总剩余 is consumer surplus plus producer surplus.
消费者剩余与生产者剩余
- 消费者剩余(consumer surplus)是需求曲线以下、价格以上的面积——买家付得比他们愿意付的少。
- 生产者剩余(producer surplus)是供给曲线以上、价格以下的面积——卖家收到的比他们愿意接受的多。
- 两者都是三角形,所以每块面积是 $\tfrac{1}{2} \times \text{base} \times \text{height}$。
- 总剩余(total surplus)是消费者剩余加生产者剩余。
Consumer surplus is the area: · 消费者剩余是这样一块面积:
Consumer surplus = willingness to pay minus price, summed — below demand, above price. · 消费者剩余 = 支付意愿减去价格的加总——需求以下、价格以上。
Consumer surplus plus producer surplus equals ______ surplus. · 消费者剩余加生产者剩余等于______剩余。
Total surplus measures the whole gain from trading in the market. · 总剩余衡量市场交易带来的全部收益。
Allocative efficiency
- At the competitive equilibrium, total surplus is as large as it can be.
- This is allocative efficiency 配置效率 — resources go to what society values most.
- It happens exactly where marginal benefit 边际收益 (from the demand curve) equals marginal cost (from the supply curve).
- Make less and MB > MC (a missed gain); make more and MC > MB (a waste).
配置效率
- 在竞争均衡处,总剩余达到最大。
- 这就是配置效率(allocative efficiency)——资源流向社会最看重的地方。
- 它恰好发生在边际收益(marginal benefit,来自需求曲线)等于边际成本(来自供给曲线)之处。
- 生产更少则 MB > MC(错过收益);生产更多则 MC > MB(造成浪费)。
Allocative efficiency occurs where marginal benefit equals marginal cost. · 配置效率发生在边际收益等于边际成本之处。
At MB = MC, total surplus is maximised — the efficient quantity. · 在 MB = MC 处,总剩余最大——有效率的数量。
Work out the surpluses
- Worked idea. Demand is $P = 20 - Q$; supply is $P = 2 + Q$.
- Set them equal: $20 - Q = 2 + Q$, so $Q = 9$ and $P = 11$.
- Consumer surplus $= \tfrac{1}{2} \times 9 \times (20 - 11) = 40.5$.
- Producer surplus $= \tfrac{1}{2} \times 9 \times (11 - 2) = 40.5$, so total surplus $= 81$.
算出剩余
- 例题。 需求是 $P = 20 - Q$;供给是 $P = 2 + Q$。
- 令两者相等:$20 - Q = 2 + Q$,得 $Q = 9$、$P = 11$。
- 消费者剩余 $= \tfrac{1}{2} \times 9 \times (20 - 11) = 40.5$。
- 生产者剩余 $= \tfrac{1}{2} \times 9 \times (11 - 2) = 40.5$,所以总剩余 $= 81$。
Demand is P = 20 − Q and supply is P = 2 + Q. What is the equilibrium quantity Q? · 需求是 P = 20 − Q,供给是 P = 2 + Q。均衡数量 Q 是多少?
Set 20 − Q = 2 + Q, so 18 = 2Q and Q = 9. · 令 20 − Q = 2 + Q,得 18 = 2Q,所以 Q = 9。
With equilibrium at Q = 9 and P = 11, and demand hitting the price axis at 20, what is the consumer surplus? (area of the triangle) · 均衡在 Q = 9、P = 11,需求曲线与价格轴交于 20,消费者剩余是多少?(三角形面积)
CS = ½ × base × height = ½ × 9 × (20 − 11) = 40.5. · CS = ½ × 底 × 高 = ½ × 9 × (20 − 11) = 40.5。
Equilibrium is where supply meets demand (quantity demanded = quantity supplied). Consumer surplus (below demand, above price) plus producer surplus (above supply, below price) make total surplus, which is largest at the equilibrium — allocative efficiency, where MB = MC.
均衡是供给与需求相遇之处(需求量 = 供给量)。消费者剩余(需求以下、价格以上)加生产者剩余(供给以上、价格以下)构成总剩余,它在均衡处最大——即配置效率,此时 MB = MC。