今天讲经济学的另一个重要概念：需求弹性。还是像以往一样，我翻译的时候不会全按照原文，而是会添加一些帮助大家理解经济学的知识。我们一边学英语，一边学微观经济学。事半功倍。
在开始讲理论之前，作者引述了一个例子：如果你是卖儿童读物的，你想增加营收，你会怎么做呢？你是提高单位商品价格？还是打折促销？
答案是，问问你当经济学家的朋友。（开个玩笑。）而她可能又会抛出那句老话：看情况。
我们先直观的想，想赚钱当然是提价了，每本书我卖的越贵不就挣的越多吗？还记得我们之前讲过的需求原理吗？它告诉我们，你提高商品价格，那买的人自然就会少了，顾客很可能就跑去隔壁街上更远的那家书店去了，因为更便宜。那你说，好吧，那我就打折促销，这样买的人多了，我总能赚到了吧？可是打折，我到底该定多少的折扣来吸引顾客，同时又能保证不亏本还赚钱呢？
我们来看看现实生活中的例子，一个卖电子产品的商店，可能会提价来盈利；同时呢，一家航空公司反而是对机票打折来赚取盈利。哪个做法对呢？
答案是，两种做法都对。
还记得我们之前讲过的需求曲线吗？随着价格的波动，需求不变，需求量会沿着曲线上下移动。但需求曲线并没有准确的告诉我们，随着价格的变动，需求量的精确数据变化。理论是没错的，可我们怎么用它来指导实践呢？
原文如下：
Elasticity of Demand 1
来源: 作者Dr. Mary J. McGlasson
There are many types of elasticity; in particular I'll focus on the price elasticity of demand.
Before I get into a specific discussion of elasticity, let me ask you a question:
if a business wants to generate more revenue, should it raise the price of its product, or lower the price of its product?
I ask because I have a friend who runs a children's bookstore, and when she found out that I was economist, she asked me this question.
Well actually, she asked if she should be giving an educator discount, but what this really meant was that she wanted to know if she should discount (or lower) her prices.
So generally, what would you say?
Should a business owner increase prices, or decrease prices in order to generate more revenue?
The answer, as usual, is "it depends."
Think about it: when your local electric company wants to raise more revenue, it will enact a rate increase.
Yet when an airline wants to quickly generate additional revenue, it will cut ticket prices.
Which approach is correct?
They both are.
Here's the issue: if I raise my prices, I know that quantity demanded, or the willingness to purchase on the part of my consumers, will drop.
That's just the Law of Demand.
But what the Law of Demand doesn't tell me is how much the quantity demanded will drop.
When I raise my price, will my customers be very sensitive to the price increase, cutting back a lot on their purchases?
This would be bad for me, because I would lose a lot of revenue.
But if I raise my price, and my customers only by a little bit less, not reacting too much to the price increase, this is good; I'd see increased overall revenue.
So the crucial issue here is to find out how sensitive my customers will be to a price change.
