Elasticity is a term used a lot in economics todescribe the way one thing changes in a givenenvironment in response to another variable thathas a changed value.
For example, the quantity of a specific product soldeach month changes in response to themanufacturer alters the product's price.
例如，每个月销售的特定产品的数量随着厂商改变产品的价格而变化。
A more abstract way of putting it that means pretty much the same thing is that elasticitymeasures the responsiveness of one variable in a given environment to a change in anothervariable, which in this instance is a change in price.
更为抽象的说法，弹性衡量的是给定环境中一个变量对另一个变量变化的响应性，在这个例子中是价格变化。
Or you could also say it measures "the sensitivity" of that variable.
或者你也可以说它测量了这个变量的“灵敏度”。
Often, e conomists speak of a demand curve, where the relationship between price and demandvaries depending upon how much or how little one of the two variables is changed.
通常，经济学家说的是需求曲线，即价格和需求之间的关系取决于两个变量中的一个变化了多少。
Some Examples of Elasticity and Inelasticity
弹性和非弹性的一些例子
It's not surprising when a manufacturer substantially increases a product's price, that consumerdemand should diminish.
当制造商大幅度提高产品价格时，消费者的需求就会减少，这不足为奇。
Many common items, such as aspirin, are widely available from any number of sources.
许多常见物品，如阿司匹林，可以从许多来源广泛获得。
In such cases, the product's maker raises the price at its own risk -- if the price rises even alittle, some shoppers might stay loyal to the specific brand -- at one time, Bayer nearly had alock on the U.S. aspirin market -- but many more consumers would probably seek the sameproduct from another manufacturer at the lower price.
In such instances, the demand for the product is highly elastic and such instances e conomistsnote a high sensitivity of demand.
在这种情况下，对产品的需求是高度弹性的，经济学家注意到了需求的高度敏感性。
But in other instances, the demand is not elastic at all.
但在其他情况下，需求根本不具有弹性。
Water, for example, is usually supplied in any given municipality by a single quasi-governmental organization, often along with electricity.
例如，在任何特定的城市，水通常由一个单一的准政府组织供应，通常与电力一起供应。
When something consumers use daily, such as electricity or water, has a single source, thedemand for the product may continue even as the price rises -- basically, because the consumerhas no alternative.
Another strange phenomenon in price/demand elasticity in the 21st century has to do withthe Internet.
21世纪价格/需求弹性的另一个奇怪现象与互联网有关。
The New York Times has noted, for instance, that Amazon often changes prices in ways that arenot directly responsive to demand, but rather to the ways consumers order the product -- aproduct that cost X when initially ordered may be filled at X-plus when reordered, often whenthe consumer has initiated automatic re-ordering.
The actual demand, presumably, hasn't changed, but the price has.
实际需求可能没有发生变化，但是价格已经改变了。
Airlines and other travel sites commonly change the price of a product based on an algorithmicestimation of some future demand, not a demand that actually exists when the price ischanged.
Some travel sites, USA and others have noted, put a cookie on the consumer's computer whenthe consumer first inquires about the cost of a product; when the consumer checks again, thecookie raises the price, not in response to a general demand for the product, but in responseto a single consumer's expression of interest.
These situations do not at all invalidate the principle of price elasticity of demand. Ifanything, they confirm it, but in interesting and complicated ways.
Price/demand elasticity for common products is generally high.
普通产品的价格/需求弹性通常很高。
Price/demand elasticity where the good has only a single source or a very limited number ofsources is typically low.
当商品只有单一来源或来源数量非常有限时，价格/需求弹性通常很低。
External situations may create rapid changes in the price elasticity of demand for almost anyproduct with low elasticity.
外部环境可能会导致几乎所有低弹性产品的需求价格弹性的快速变化。
Digital capabilities, such as "demand pricing" on the Internet, can affect price/demand in waysthat were unknown in the 20th century.
数字能力，例如互联网上的“需求定价”，可以以20世纪未知的方式影响价格/需求。
How to Express Elasticity as a Formula
如何用公式表达弹性
Elasticity, as an economics concept,can be applied to many different situations, each with itsown variables. In this introductory article, we've briefly surveyed the concept of the priceelasticity of demand. Here's the formula:
