理想状态下的市场能够达到高效生产：将总剩余(total surplus)最大化。 但是在现实中的市场并非完美。在本课程中，我们将探索一系列市场存在着缺陷的情形并且理解为什么会出现这些缺陷；同时，我们会了解一些改进措施，比如反托拉斯(antitrust)政策以及其他一些政府的干预措施。 我们会选取日常中的例子——从我们每天购买和享用的货物和服务开始。我们也会在每周的练习里把理论运用到时下大事和政策研讨中。 所有的这些都会使你成为一个可以理解、分析和评价市场结果的，有学识的，有批判精神的思考者。

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来自 University of Pennsylvania 的课程

微观经济学：当市场“失灵”时

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理想状态下的市场能够达到高效生产：将总剩余(total surplus)最大化。 但是在现实中的市场并非完美。在本课程中，我们将探索一系列市场存在着缺陷的情形并且理解为什么会出现这些缺陷；同时，我们会了解一些改进措施，比如反托拉斯(antitrust)政策以及其他一些政府的干预措施。 我们会选取日常中的例子——从我们每天购买和享用的货物和服务开始。我们也会在每周的练习里把理论运用到时下大事和政策研讨中。 所有的这些都会使你成为一个可以理解、分析和评价市场结果的，有学识的，有批判精神的思考者。

从本节课中

Monopoly

A monopoly is a case where there is only one firm in the market. We will define and model this case and explain why market power is good for the firm, bad for consumers. We will also show that society as a whole suffers from the lack of competition.

- Rebecca SteinSenior Lecturer

Economics

[MUSIC]

I'd like us to go through the profit maximizing quantity and price for

a monopolist with a specific numeric example.

Let's continue with the demand curve that I introduced earlier, P = 150- Q.

So it's a linear straight line demand curve with an intercept of 150.

And this implies that the MR = 150- 2Q.

So again, the marginal revenue lies below the demand curve and

its steeper than the demand curve.

Because every time you lower the price, you have to give a discount on bigger and

bigger previous quantities.

So we have the demand curve, and we have the marginal revenue curve,

we need to introduce the cost structure for the firm.

So here is the total cost function.

TC = 1,000 + .5Q squared.

So of course, this is the fixed cost of production

because this is the amount that is not dependent on quantity.

And these are the total variable cost because they are dependent on quantity,

and they increase as quantity increases.

We can derive the marginal cost curve.

It's the derivative of the total cost with respect to quantity, or

if you don't like calculus, just believe me the MC = Q.

If we had to draw this marginal cost curve it would be an upward sloping line.

That looks something like this.

So, this marginal cost curve is missing the part that first goes down, and

then increases.

But in some sense we can disregard that part, because we know the firm is

never going to produce at the point that is below the average variable cost.

So again, here's a numerical example, downward sloping demand curve,

downward sloping marginal revenue curve, upward sloping marginal cost curve,

so let's go ahead and solve for the monopolist quantity and price.

Finding the profit maximizing output is

setting marginal revenue equal to marginal costs.

In this case, it's 150- 2Q = Q,

or solving for Q we get that the monopolist output is equal to 50.

So suppose this firm is making jeans their monopoly output is where marginal costs

equals marginal revenue, and the firm should go ahead and produce 50 units.

And what is the price?

We have to take this quantity and plug it back into the demand curve,

so that the pm=150-50.

It's equal to $100 per unit.

Graphically what we're doing is we're taking this quantity, plugging it back

into the demand curve, and we get that the price is equal to $100.

This is the profit maximizing output and price.

We can go ahead and calculate profits if we want.

We know that profits are equal to revenue minus total

cost of revenue is 50 times 100 of 5000.

And what our costs?

We're given the total cost curve here, we have the fixed cost of a 1000,

and we have the variable cost which are .5 times a quantity of 50 squared.

And we could go ahead and calculate this if we wish.