Understand the Economic Concept of a Budget Line
理解预算线的经济学概念

The term“budget line”has several related meanings, including a couple that are self-evident and a third that is not.
“预算线”这个词有几个相关的含义，包括两个显而易见的和一个不那么明显的。

The budget line as an Informal Consumer Understanding
预算线作为非正式消费者理解

The budget line is an elementary concept that most consumers understand intuitively without a need for graphs and equations—it’s the household budget, for example.
预算线是一个基本概念，大多数消费者在没有图表和方程式的情况下也能直观理解——例如家庭预算。

Taken informally, the budget line describes the boundary of affordability for a given budget and specific goods.
从非正式的角度来看，预算线描述了在特定预算和商品下可负担的范围。

Given a limited amount of money, a consumer can only spend that same amount buying goods. If the consumer has X amount of money and wants to buy two goods A and B, she can only purchase goods totaling X. If the consumer needs an amount of A costing 0.75, she can then spend only 0.25 X, the amount remaining, on her purchase of B.
考虑到有限的资金，消费者只能花费相同金额购买商品。如果消费者有X金额的钱，想要购买两种商品A和B，她只能购买总计X金额的商品。如果消费者需要购买A商品，花费0.75X，那么她只能花费剩余的0.25X购买B商品。

This seems almost too obvious to bother writing or reading about. As it turns out, however, this same concept-one that most consumers make many times each day with reflecting on it-is the basis of the more formal budget line concept in economics, which is explained below.
这看起来几乎太明显了，不值得写或读。然而，事实上，这个相同的概念——大多数消费者每天多次考虑的非正式理解——是经济学中更正式预算线概念的基础，下面将进行解释。

Lines in a Budget
预算中的线条

Before turning to the economics definition of budget line, consider another concept: the line-item budget. This is effectively a map of future expenditures, with all the constituent expenditures individually noted and quantified. There’s nothing very complicated about this usage, a budget line is one of the lines in the budget, with the service or good to be purchased named and the cost quantified,
在转向预算线的经济学定义之前，考虑另一个概念：项目预算。这实际上是未来支出的地图，所有组成的支出都被单独记录和量化。这种用法没有什么复杂的，预算线是预算中的一条线，列出了要购买的服务或商品及其成本。

The Budget Line as an Economics Concept
预算线作为经济学概念

One of the interesting ways the study of economics relates to human behavior generally is that a lot of economic theory is the formalization of the kind of simple concept outlined above—a consumer’s informal understanding of the amount she has to spend and what that amount will buy.
经济学研究与一般人类行为相关的一个有趣方式是，许多经济理论都是对上述简单概念的正式化——消费者对她要花费的金额及其购买力的非正式理解。

In the process of formalization, the concept can be expressed as a mathematical equation that can be applied generally.
在正式化的过程中，这个概念可以表达为一个数学方程，可以普遍应用。

A Simple Budget Line Graph
一个简单的预算线图

To understand this, think of a graph where the vertical lines quantify how many movie tickets. you can buy and where the horizontal lines do the same for crime novels. You like going to the movies and reading crime novels and you have $ 150 to spend, In the example below, assume that each movie costs $10 and each crime novel costs $15. The more formal economics term for these two items is budget set.
为了理解这一点，想象一个图表，其中垂直线量化了你可以购买的电影票数量，水平线则为犯罪小说。你喜欢看电影和阅读犯罪小说，你有150美元可以花费。在下面的示例中，假设每部电影10美元，每本犯罪小说15美元。这两个项目的更正式的经济学术语是预算集。

If movies cost $ 10 each, then the maximum number of movies you can see with the money available is 15. To note this you make a dot at the number 15(for total movie tickets) at the extreme left-hand side of the chart. This same dot appears at the extreme left above“0”on the horizontal axis because you have no money left for books—the number of books available in this example is 0. You can also graph the other extreme —all crime novels and no movies. Since crime novels in the example cost $15 and you have $150 available, if you spend all the available money crime novels, you can buy 10. So you put a dot on the horizontal axis at the number 10.
如果电影票价为每部10美元，那么你最多可以观看的电影数量是15部。为了标记这一点，你会在图表的最左侧的15（代表总电影票数）处画一个点。同样的点也会出现在水平轴的极端左侧，即“0”的上方，因为你没有剩余的钱来购买书籍——在这个例子中，可购买的书籍数量为0。你也可以画出另一个极端——全部购买犯罪小说而不看电影。由于犯罪小说在这个例子中的价格是15美元，而你有150美元的预算，如果你将所有可用的钱都用来购买犯罪小说，你可以购买10本。所以你会水平轴上的数字10处画一个点。

You’ll place the dot at the bottom of the vertical axis because in this instance you have $0 available for movie tickets.
你会在垂直轴的底部放置这个点，因为在这种情况下，你没有钱可用于购买电影票。

If you now draw a line from the highest, leftmost dot to the lowest, rightmost dot you’ll have created a budget line. Any combination of movies and crime novels that falls below the budget line is affordable. Any combination above it is not.
如果你现在从最高点的左点画一条线到最低点的右点，你就会创建一个预算线。任何落在预算线以下的犯罪小说和电影的组合都是负担得起的。任何组合在上面的都是负担不起的。

1. Which sentence about the budget line is NOT TRUE?
   A. It is limitation of affordability for a given budget and specific goods.
   B. Most costumers will be confused with this concept because of its complex.
   C. It is the effectively a map of future expenditures.
   D. It can be expressed as a mathematical. equation.
   答案：B

1. What is the purpose of the passage?
   A. To tell us any concept can be expressed as a mathematical equation.
   B. To help us figure out the meaning Budget Line.
   C. To tell us we should budget before we buy goods.
   D. To give an instruction of drawing a budget Line.
   答案：B

2. Assume that each movie costs 10 and each crime novel costs, $15, you have$150. Which is RIGHT according to this passage?
   A. The maximum number of movies you can see is 10.
   B. The maximum number of crime novels you can buy is 15.
   C. You can buy 7 crime novels and, see 5 movies.
   D. You can buy 7 crime novels and see 4 movies.
   答案：D

   1. What is the best title of this passage?
      A. Do we really know the economic concept of a budget line?
      B. The Budget Line as an Economics Concept.
      C. The Budget Line as an Informal Consumer Understanding
      D. The Complex Concept-Budget Line
      答案：A