Price Elasticity of Supply | 供给价格弹性解析

📚 Price Elasticity of Supply | 供给价格弹性解析

Price Elasticity of Supply (PES) measures how responsive the quantity supplied of a good is to a change in its price. It is a fundamental concept in IGCSE Economics that helps explain producer behaviour and market dynamics.

供给价格弹性（PES）衡量的是商品供给量对其价格变动的反应程度。这是 IGCSE 经济学中的一个核心概念，有助于解释生产者行为和市场动态。

1. Definition and Formula | 定义与公式

Price Elasticity of Supply is defined as the percentage change in quantity supplied divided by the percentage change in price. It tells us whether producers can respond quickly or slowly to price changes in the market.

供给价格弹性定义为供给量的百分比变化除以价格的百分比变化。它告诉我们生产者在面对市场价格变化时能够快速还是缓慢地作出反应。

PES = % Change in Quantity Supplied ÷ % Change in Price

For example, if the price of a good rises by 10% and the quantity supplied increases by 20%, the PES would be 2. This means supply is elastic and producers respond strongly to price changes.

例如，如果某种商品的价格上涨 10%，而供给量增加了 20%，那么 PES 就是 2。这意味着供给是富有弹性的，生产者对价格变化反应强烈。

2. The Five Types of Supply Elasticity | 供给弹性的五种类型

PES values can range from zero to infinity, and economists classify supply into five distinct categories. Each category reflects a different degree of producer responsiveness.

PES 的数值可以从零到无穷大，经济学家将供给分为五个不同的类别。每个类别都反映了生产者不同程度的反应性。

Perfectly Inelastic Supply (PES = 0): Quantity supplied does not change at all when price changes. This applies to goods with a fixed supply, such as seats in a stadium or original works of art.

完全无弹性供给（PES = 0）：当价格变化时，供给量完全不变。这适用于供给固定的商品，例如体育场的座位或原创艺术品。
Inelastic Supply (0 < PES < 1): Quantity supplied changes proportionally less than the price change. Agricultural products in the short run often fall into this category.

缺乏弹性供给（0 < PES < 1）：供给量的变化比例小于价格的变化比例。短期内的农产品通常属于这一类。
Unit Elastic Supply (PES = 1): Quantity supplied changes by the exact same percentage as the price change. This is rare in the real world but serves as an important benchmark.

单位弹性供给（PES = 1）：供给量的变化百分比与价格的变化百分比完全相同。这在现实世界中很少见，但作为一个重要的基准。
Elastic Supply (PES > 1): Quantity supplied changes proportionally more than the price change. Manufactured goods with spare capacity often exhibit this behaviour.

富有弹性供给（PES > 1）：供给量的变化比例大于价格的变化比例。具有闲置产能的制成品通常表现出这种行为。
Perfectly Elastic Supply (PES = ∞): Any tiny price increase causes quantity supplied to become infinite. This occurs in highly competitive markets with firms that can supply any amount at a given price.

完全弹性供给（PES = ∞）：任何微小的价格上升都会使供给量变为无穷大。这发生在竞争激烈的市场中，厂商可以在给定价格下供给任意数量。

3. The Role of Time Period | 时间因素的作用

Time is the single most important factor influencing the price elasticity of supply. In general, supply becomes more elastic as more time passes, because producers need time to adjust their production plans and resources.

时间是影响供给价格弹性最重要的单一因素。一般来说，随着时间推移，供给会变得更有弹性，因为生产者需要时间来调整他们的生产计划和资源。

In the immediate short run, supply is often perfectly inelastic. A farmer cannot instantly produce more wheat when prices rise, because crops require months to grow. Similarly, a factory cannot double its output overnight without additional machinery or labour.

在极短期内，供给通常是完全无弹性的。当价格上涨时，农民无法立即生产更多小麦，因为作物需要数月才能生长。同样，工厂没有额外的机器或劳动力，也无法在一夜之间将产量翻倍。

In the short run, producers can increase output to some extent by using existing capacity more intensively — for example, paying overtime to workers or using raw materials already held in stock. This makes supply somewhat elastic, though still limited.

在短期内，生产者可以通过更密集地利用现有产能来增加产出——例如，向工人支付加班费或使用库存中的原材料。这使供给具有一定弹性，但仍然有限。

In the long run, supply becomes highly elastic. Firms can build new factories, train additional workers, and invest in new technology. New firms can also enter the industry, further increasing the market’s ability to respond to price changes.

在长期内，供给变得高度有弹性。企业可以建造新工厂、培训更多工人并投资新技术。新企业也可以进入该行业，进一步增强市场应对价格变化的能力。

4. Factors Influencing PES | 影响供给价格弹性的因素

Beyond time, several other factors determine whether a product’s supply is elastic or inelastic. Understanding these factors allows economists to predict producer behaviour and market outcomes.

除了时间之外，还有其他几个因素决定一种产品的供给是有弹性还是缺乏弹性。理解这些因素使经济学家能够预测生产者行为和市场结果。

Spare Capacity | 闲置产能：If firms have unused factories, machines, or labour, they can quickly increase output when price rises, making supply more elastic. Conversely, if a firm is already producing at full capacity, supply will be inelastic.

如果企业拥有未使用的工厂、机器或劳动力，它们可以在价格上涨时迅速增加产出，使供给更有弹性。相反，如果企业已经在满负荷生产，供给将缺乏弹性。

Availability of Stocks | 库存的可用性：Producers holding large inventories of finished goods can immediately release them onto the market when prices rise. This makes supply elastic. Firms with minimal or zero stocks show more inelastic supply.

持有大量成品库存的生产者在价格上涨时可以立即将库存投放市场。这使供给具有弹性。库存极少或没有库存的企业则表现出更缺乏弹性的供给。

Speed of Production | 生产速度：Goods that can be produced quickly — such as fast-moving consumer goods — tend to have more elastic supply. Products requiring long production processes, such as ships or large-scale construction, have more inelastic supply.

能够快速生产的商品——例如快速消费品——往往具有更有弹性的供给。需要漫长生产流程的产品，如船舶或大型建筑，则具有更缺乏弹性的供给。

Factor Mobility | 生产要素的流动性：When capital and labour can be easily transferred from one use to another, supply is more elastic. Difficulty in switching resources makes supply inelastic.

当资本和劳动力可以轻松地从一种用途转移到另一种用途时，供给更有弹性。资源转换的困难使供给缺乏弹性。

Number of Producers | 生产者数量：Industries with many independent producers tend to have more elastic supply, as individual firms can respond independently to price signals. Monopolies or oligopolies often show more inelastic supply behaviour.

拥有许多独立生产者的行业往往具有更有弹性的供给，因为个别企业可以独立地对价格信号作出反应。垄断或寡头垄断通常表现出更缺乏弹性的供给行为。

Difficulty of Storage | 储存的难度：Perishable goods, such as fresh fruit and dairy products, are difficult to store and therefore have inelastic supply. Goods that can be easily and cheaply stored — like canned foods — have more elastic supply.

易腐烂的商品，如新鲜水果和乳制品，难以储存，因此供给缺乏弹性。容易且廉价储存的商品——如罐头食品——则具有更有弹性的供给。

5. Interpreting PES Values | 解读 PES 数值

Calculating PES is straightforward, but interpreting the result correctly requires care. The sign of PES is always positive because price and quantity supplied move in the same direction — this reflects the law of supply.

计算 PES 并不复杂，但正确解读结果需要谨慎。PES 的符号始终为正，因为价格和供给量朝同一方向变动——这反映了供给法则。

When examining PES, we ignore the plus sign and focus on the magnitude. A value greater than 1 indicates elastic supply, while a value less than 1 indicates inelastic supply. Values closer to zero suggest that price changes have very little effect on the quantity supplied.

在考察 PES 时，我们忽略正号而关注数值大小。大于 1 的数值表示供给富有弹性，而小于 1 的数值表示供给缺乏弹性。越接近零的数值表明价格变化对供给量的影响越小。

It is important to remember that PES is not constant for all price ranges of a single product. At very low output levels, firms may have significant spare capacity, making supply elastic. As output approaches full capacity, supply becomes increasingly inelastic.

重要的是要记住，PES 对单一产品的所有价格区间并不恒定。在非常低的产出水平下，企业可能拥有大量闲置产能，使供给具有弹性。随着产出接近满负荷，供给变得越来越缺乏弹性。

6. Worked Example | 计算示例

Consider a mobile phone manufacturer. When the price of a particular model rises from 500 to 600 pounds, the firm increases its weekly output from 2,000 to 2,600 units. Let us calculate the PES.

考虑一家手机制造商。当某型号手机的价格从 500 英镑上涨到 600 英镑时，该企业将每周产量从 2,000 部增加到 2,600 部。让我们计算 PES。

Step 1: Calculate the percentage change in price | 第1步：计算价格变化百分比

%ΔP = (600 − 500) ÷ 500 × 100 = 20%

Step 2: Calculate the percentage change in quantity supplied | 第2步：计算供给量变化百分比

%ΔQS = (2,600 − 2,000) ÷ 2,000 × 100 = 30%

Step 3: Calculate PES | 第3步：计算 PES

PES = 30% ÷ 20% = 1.5

Since PES = 1.5, which is greater than 1, this firm’s supply is price elastic. The firm responded proportionally more than the price change, likely because it had spare capacity to increase production quickly.

由于 PES = 1.5，大于 1，该企业的供给是富有价格弹性的。企业对价格变化的反应比例大于价格变化本身，很可能是因为它拥有闲置产能来快速增加生产。

7. Applications and Importance | 应用与重要性

Understanding PES has significant real-world implications for businesses, governments, and consumers alike. It helps predict how markets adjust to shocks and informs policy decisions.

理解 PES 对企业、政府和消费者都具有重要的现实意义。它有助于预测市场如何应对冲击，并为政策决策提供信息。

For Producers | 对生产者：Firms need to know their PES to plan production schedules and pricing strategies. If supply is inelastic, a rise in demand will push up prices significantly, potentially benefiting producers in the short run but risking consumer backlash.

企业需要了解其 PES 以规划生产安排和定价策略。如果供给缺乏弹性，需求的上升将显著推高价格，短期内可能使生产者受益，但也可能引发消费者的反对。

For Government Policy | 对政府政策：When governments impose indirect taxes, the incidence of the tax depends on both PES and price elasticity of demand. If supply is inelastic, producers bear a larger share of the tax burden; if supply is elastic, they can shift more of the tax onto consumers.

当政府征收间接税时，税收的归宿取决于 PES 和需求价格弹性。如果供给缺乏弹性，生产者承担更大的税收份额；如果供给富有弹性，他们可以将更多税收转嫁给消费者。

For Agricultural Markets | 对农产品市场：Agricultural products typically have inelastic supply in the short run due to growing seasons. When demand rises or falls, prices fluctuate dramatically. Governments may intervene with subsidies or price stabilisation schemes to protect farmers and consumers.

由于生长周期的原因，农产品在短期内通常具有缺乏弹性的供给。当需求上升或下降时，价格会剧烈波动。政府可能会通过补贴或价格稳定计划进行干预，以保护农民和消费者。

8. Common Exam Mistakes and Tips | 常见考试错误与提示

Students often lose marks in IGCSE Economics exams by confusing PES with price elasticity of demand. Remember that PES deals with the producer’s response, while PED measures the consumer’s response.

学生在 IGCSE 经济学考试中经常因为混淆 PES 与需求价格弹性而失分。记住 PES 涉及生产者的反应，而 PED 衡量的是消费者的反应。

Always show the full formula in calculations and include the percentage signs. Marks are typically awarded for showing method, not just the final answer.

在计算中始终展示完整公式并包含百分号。分数通常是根据展示的解题过程而非最终答案来评定的。
When drawing PES diagrams, ensure the supply curve is steep for inelastic supply and relatively flat for elastic supply. Both curves pass through the origin to represent elasticity at a point.

在绘制 PES 图形时，确保缺乏弹性的供给曲线较陡，富有弹性的供给曲线相对平缓。两条曲线都通过原点以表示在某一点的弹性。
Use real-world examples in essay questions. Mentioning perishable goods for inelastic supply or manufactured goods with spare capacity for elastic supply demonstrates deeper understanding.

在论述题中运用现实世界的例子。提到易腐烂商品作为缺乏弹性供给的例子，或用闲置产能的制成品作为富有弹性供给的例子，能够展示更深层次的理解。
Do not forget to discuss the time dimension. Examiners expect candidates to explain that supply becomes more elastic over time, even for the same product.

不要忘记讨论时间维度。考官期望考生解释即使对于同一种产品，供给也会随着时间的推移变得更有弹性。
Identify the “direction of the shift” carefully in application questions. A change in price causes a movement along the supply curve, while changes in non-price factors shift the entire supply curve.

在应用题中仔细辨别”移动的方向”。价格变化引起沿供给曲线的移动，而非价格因素的变化则使整条供给曲线发生位移。

Published by TutorHao | Economics Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）

Price Elasticity of Supply | 供给价格弹性解析