Partial Equilibrium vs General Equilibrium Analysis | 局部均衡与一般均衡分析

📚 Partial Equilibrium vs General Equilibrium Analysis | 局部均衡与一般均衡分析

In economics, markets do not exist in separate boxes. A rise in the price of beef changes the demand for chicken; a new technology in car production changes the demand for steel and the wages of automotive workers. At exam level, you need to know two distinct ways of describing the resulting equilibrium: partial equilibrium and general equilibrium. The first isolates one market; the second models all markets together.

在经济学中，市场并非彼此隔绝。牛肉价格上涨会改变鸡肉的需求；汽车生产的新技术会改变对钢铁的需求以及汽车工人的工资。在考试中，你需要掌握两种描述均衡的方式：局部均衡与一般均衡。前者把单一市场隔离出来分析，后者把所有市场放在一起建模。

1. A World of Interconnected Markets | 相互关联的市场世界

Markets are connected through prices and incomes. When the price of crude oil rises, the cost of using a car increases, the demand for rail travel rises, and the price of plastics and electricity may also change. These links are not random exceptions; they are normal features of an economy. Any single-market analysis must therefore decide whether the links are important enough to matter.

市场通过价格和收入相互关联。原油价格上升时，开车成本增加，铁路出行需求上升，塑料与电力价格也可能发生变化。这些联系不是偶然的例外，而是经济运行的常态。因此，单一市场分析必须判断这些联系是否重要到无法忽略。

2. Partial Equilibrium Analysis | 局部均衡分析

Partial equilibrium analysis was popularised by Alfred Marshall. It examines one market, for example the market for fresh milk, and treats the rest of the economy as constant. The equilibrium price and quantity are found where the market demand curve intersects the market supply curve. All variables outside that market, such as the price of other goods, wages and consumer incomes, are assumed to stay unchanged. The word “partial” is the key signal: the market is seen as only a small part of the whole.

局部均衡分析由阿尔弗雷德·马歇尔推广。它只考察一个市场，例如鲜奶市场，并把经济中的其他部分视为不变。均衡价格和数量由市场需求曲线与市场供给曲线的交点决定。该市场之外的一切变量，如其他商品价格、工资和消费者收入，都被假定保持不变。“局部”是关键信号：这个市场只被视为整体中的一小部分。

The key assumption is ceteris paribus: all other things stay equal. We ask one limited question: what single market price and quantity clear this market? This is why a simple supply-and-demand diagram is usually a partial equilibrium diagram. The diagram does not show what happens to substitute goods, factor incomes, or the general price level.

这里的关键假设是 ceteris paribus，即其他条件不变。我们只问一个有限的问题：这个市场的均衡价格和均衡数量是多少？因此，简单的供给需求图通常就是局部均衡图。图中并不展示替代品、要素收入或总体价格水平会发生什么变化。

3. Worked Partial Equilibrium Example | 局部均衡实例

Take a simple linear demand and supply model for a market:

Qd = 100 − 2P, Qs = 20 + 3P

Setting Qd = Qs gives 100 − 2P = 20 + 3P, so P = 16 and Q = 68. This is a partial equilibrium solution

Published by TutorHao | Economics Revision Series | aleveler.com

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