1塊錢如何花成2塊錢？你得學會Marginal Analysis
From an e conomist's perspective, making choices involves making decisions 'at the margin' -- that is, making decisions based on small changes in resources:
從經濟學家的角度來看，做出選擇包括“在邊際”做出決定——也就是說，根據資源的微小變化做出決定：
How should I spend the next hour?
我該如何度過接下來的一個小時?
How should I spend the next dollar?
下一美元該怎麼花?
In fact, e conomist Greg Mankiw lists under the "10 principles of economics" in his popular economics textbook the notion that "rational people think at the margin." On the surface, this seems like a strange way of considering the choices made by people and firms.
事實上，經濟學家格雷格·曼昆在他廣受歡迎的經濟學教科書中的“經濟學的十大原則”下列出了“理性的人在邊緣思考”。從表面上看，這似乎是一種奇怪的方式來考慮人們和公司做出的選擇。
It is rare that someone would consciously ask themselves -- "How will I spend dollar number 24,387?" or "How will I spend dollar number 24,388?" The idea of marginal analysis doesn't require that people explicitly think in this way, just that their actions are consistent with what they would do if they did think in this way.
很少有人會有意識地問自己——“我將如何花24,387美元?”或者“我將如何花24,388美元?”邊際分析的思想並不要求人們明確地以這種方式思考，只要求他們的行爲與他們以這種方式思考會做的事情是一致的。
Marginal analysis can be applied to both individual and firm decision making.
邊際分析既適用於個人決策，也適用於企業決策。
For firms, profit maximization is achieved by weighing marginal revenue versus marginal cost.
對於企業來說，利潤最大化是通過權衡邊際收益與邊際成本來實現的。
For individuals, utility maximization is achieved by weighing the marginal benefit versus marginal cost. Note, however, that in both contexts the decision maker is performing an incremental form of cost-benefit analysis.
對個人來說，效用最大化是通過權衡邊際效益和邊際成本來實現的。但請注意，在這兩種情況下，決策者都在執行一種增量形式的成本效益分析。
Let’s see an example:
讓我們來看一個例子：
To gain some more insight, consider the decision regarding how many hours to work, where the benefits and costs of working are designated by the following chart:
爲了更深入的瞭解，我們來權衡一下關於工作時間的決定，工作的收益和成本是由下面的圖表指定的:
Hour - Hourly Wage - Value of Time
工作時間 - 每小時的工資 - 時間的價值
Hour 1: $10 - $2
Hour 2: $10 - $2
Hour 3: $10 - $3
Hour 4: $10 - $3
Hour 5: $10 - $4
Hour 6: $10 - $5
Hour 7: $10 - $6
Hour 8: $10 - $8
Hour 9: $15 - $9
Hour 10: $15 - $12
Hour 11: $15 - $18
Hour 12: $15 - $20
The hourly wage represents what one earns for working an extra hour - it is the marginal gain or the marginal benefit.
每小時的工資代表了一個人額外工作一小時的收入——這是邊際收益或邊際效益。
The value of time is essentially an opportunity cost -- it is how much one values having that hour off. In this example, it represents a marginal cost -- what it costs an individual to work an additional hour. The increase in marginal costs is a common phenomenon; one usually doesn't mind working a few hours since there are 24 hours in a day. She still has plenty of time to do other things. However, as an individual starts to work more hours, it reduces the number of hours she has for other activities. She has to start giving up more and more valuable opportunities to work those extra hours.
時間的價值本質上是一個機會成本——它是一個人休息一個小時的價值。在這個例子中，它代表了邊際成本——一個人額外工作一小時的成本。邊際成本的增加是一個普遍現象；人們通常不介意工作幾個小時，因爲一天有24小時，她還有足夠的時間做其他事情。然而，當一個人開始工作更長時間時，這就減少了她從事其他活動的時間。她不得不開始放棄越來越多的寶貴機會來加班。
It is clear that she should work the first hour, as she gains $10 in marginal benefits and loses only $2 in marginal costs, for a net gain of $8.
顯然，她應該在第一個小時工作，因爲她的邊際收益是10美元，而邊際成本只有2美元，淨收益是8美元。
By the same logic, she should work the second and third hours as well. She will want to work until the time at which the marginal cost exceeds the marginal benefit. She will also want to work the 10th hour as she receives a net benefit of $3 (marginal benefit of $15, marginal cost of $12). However, she will not want to work the 11th hour, as the marginal cost ($18) exceeds the marginal benefit ($15) by three dollars.
按照同樣的邏輯，她也應該在第2和第3個小時工作。她會一直工作到邊際成本超過邊際效益的時候。到第10個小時的時候她還是願意工作，因爲她的淨收益爲3美元(邊際收益爲15美元，邊際成本爲12美元)。然而，第11個小時的工作她就不會願意做了，因爲邊際成本(18美元)比邊際效益(15美元)還要高出3美元。
Thus marginal analysis suggests that rational maximizing behavior is to work for 10 hours. More generally, optimal outcomes are achieved by examining marginal benefit and marginal cost for each incremental action and performing all of the actions where marginal benefit exceeds the marginal cost and none of the actions where marginal cost exceeds the marginal benefit. Because marginal benefits tend to decrease as one does more of an activity but marginal costs tend to increase, the marginal analysis will usually define a unique optimal level of activity.
因此，邊際分析表明，合理的最大化行爲是工作10小時。更籠統的說，通過檢查每個增量行動的邊際效益和邊際成本，並執行邊際效益超過邊際成本的所有行動，以及邊際成本沒有超過邊際效益的任何行動，均可獲得最佳結果。因爲邊際收益會隨着一項活動的增加而減少，而邊際成本卻增加，因此邊際分析通常會定義一個唯一的最佳活動水平。
（翻譯：雅蘭）
