边际思考与沉没成本谬误

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在经济学中

你会经常听到 “边际” 这个词

边际效益

边际成本

边际收益

这样的例子不胜枚举

那么经济学家认为边际是什么呢？

为什么很重要呢？

边际只是多一点或少一点的意思

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我们想象一下你正在看一部电影

而你听不到对白

你将音量稍微调高一点

[来自电影的声音]

你应该调高几多？

嗯，这是比较增加音量的

边际效益和边际成本的问题

增加一格音量听起来不错

现在你可以听到演员的对白

[声音稍微大一点]

你再增加了一格音量

[声音更大]

扬声器有点失真
但你还是比较喜欢这样子

[声音更大]

再增加一格

[声音爆炸]

嗯—哦

现在是动作场面

太大声了

你不想吵醒室友

于是你降低一格

[声音更小]

继续这样做

边际地调高调低

将每一步的边际效益与边际成本进行比较

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边际的考虑意味着

将下一个决策的效益与其成本进行比较

要注意，边际的考虑—

是达成最理想或最佳决策的一种方法或途径

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如果我问你看电影用什么音量最好

你可能难以回答

但如果你一直在边际上思考和行动

你会到达边际收益等于边际成本—

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这是最理想的情况

因此，边际思考

是寻找和找到答案的一种方式

否则可能会很难才找到问题的答案

边际思考

还告诉你一些其他重要的事情

不该考虑的事情

假设你经营一家小型服装店

而你认为 20 世纪 70 年代即将迎来复兴

我记得那些时候

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因此你买了 100 条牛仔喇叭裤

假设支付了 75 美元一条

你把牛仔裤定价为 100 美元—

这能够支付你的成本，包括租金和工资

但不幸的是，牛仔裤卖不出去

- 什么？
- 你要做什么呢？

你会考虑降价

但你的会计师告诉你

如果把售价降到 100 美元以下

你肯定会蒙受损失

[尖叫音效]

幸运的是，你在高中或大学

上过很好的经济学课

所以你记得

你为牛仔裤付的钱是无关紧要的

这是沉没成本

现在重要的是

比较你的选项的边际效益和边际成本

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One option would be to put
the jeans in storage and hope,

hope they'll come back in style.

Maybe you can get $100
per pair in the future,

but you get no money now,

plus you have to pay for storage.

Another option is to slash prices.

Sell them all now for $50 each.

That lets you clear out
your inventory

and invest in something else.

You choose option two

and invest in the next big thing:

leg warmers!

Now, I know this sounds simple,

but actually, even experienced
businesspeople --

they often focus too much
on what they paid for an item

and not enough
on their best choices right now.

It's called the sunk cost,
or fixed cost fallacy.

In fact, I snuck an example
of the fallacy right past you.

Did you catch it?

Earlier, I said you price
the jeans at $100 --

a price that will cover your costs,
including rent and wages.

But that's also wrong.

If bell-bottom jeans turn out to be
in huge demand, for example --

then you should price them
for more than $100.

What you paid for the jeans
is irrelevant --

whether your decision
was a bad one or a good one.

People fall prey
to this kind of error all the time,

especially holding on
to past mistakes.

Maybe you've been told,
"Never give up!"

Well, take the advice
of an economist.

Sometimes giving up
is the smart thing to do.

Is the movie
you're watching boring?

Well, buying the ticket
was a bad decision.

But that cost is sunk.

Don't throw good time after bad.

Walk out!

No one likes to admit
that they made a bad decision,

and so they stay
in bad relationships,

bad businesses, and bad careers,

hoping, hoping
to turn things around

and prove that their past decisions
weren't so bad after all.

An economist says,
"Ignore what you can't change.

Ignore the past.
Focus on the future."

Let's summarize
thinking on the margin.

First, think about
a little bit more

or a little bit less,

and keep going
until you'll arrive at a point

where the marginal benefits
equal the marginal costs.

That's the optimum.

Second, when making a choice,

only think about
the costs and benefits

that change with that choice.

Ignore sunk costs.

Thinking on the margin --

it's useful,

and not just for Economics classes.

But if you are teaching
an Economics class,

check out our free unit plan
that incorporates this video.

I promise, the marginal benefit
will exceed the marginal cost.

And if you're ready
to test yourself,

check out our practice questions.

Finally, if you're ready
for more microeconomics,

click for the next video.

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