Alevel经济学习A*笔记：成本和收入之成本及其曲线的工作示例（Cut it average）

A-level economics revision guides and question banks covering labour markets, supply and demand, market structure and all core economics a-level topics.

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今天带给大家Alevel经济笔记是：

成本和收入-Worked Example of Costs and their Curves

As with the last Learn-It, it is worth looking at these relationships in more detail. Look at this table below. Q is output per week for a firm making computer laser printers. The cost figures are all in pounds and rounded to the nearest pound.

与上一个 Learn-It 一样，值得更详细地研究这些关系。看看下面的这张表。Q 是一家制造计算机激光打印机的公司每周的产量。成本数字均以磅为单位并四舍五入至最接近的磅数。

Q	TFC	TVC	AFC	AVC	TC	AC	MC
0	500	0	-	-	500	-	-
1	500	100	500	100	600	600	100
2	500	180	250	90	680	340	80
3	500	250	167	83	750	250	70
4	500	310	125	78	810	202	60
5	500	380	100	76	880	176	70
6	500	470	83	78	970	162	90
7	500	580	71	83	1080	154	110
8	500	730	63	91	1230	154	150
9	500	930	56	103	1430	159	200

The first column shows the progressive units of output produced.

第一列显示了产出的渐进单位。

The second column shows total fixed costs. Notice that this figure stays the same (500) for every level of output. Remember that fixed costs do not vary with output.

第二列显示总固定成本。请注意，对于每个输出级别，该数字都保持不变（500）。请记住，固定成本不会随产出而变化。

The third column shows total variable costs. The figure is always rising but does so at slightly different rates. The rate of increase slows down a little in the middle and then picks up again towards the end (see the diagram below).

第三列显示总可变成本。这个数字一直在上升，但上升的速度略有不同。增长速度在中间稍微放慢，然后在接近尾声时再次回升（见下图）。

The fourth column shows average fixed costs. This was calculated by dividing total fixed costs by output (Q).

第四列显示平均固定成本。这是通过将总固定成本除以产出 (Q) 来计算的。

The fifth column shows average variable costs. This was calculated by dividing total variable costs by output (Q).

第五列显示平均可变成本。这是通过将总可变成本除以产出 (Q) 来计算的。

The sixth column shows total cost. This is calculated by adding TFC and TVC together.

第六列显示总成本。这是通过将 TFC 和 TVC 相加计算得出的。

The seventh column shows average cost (often called average total cost). This is the average of the total cost, so we divide total cost by output (Q). You could also work it out by adding AFC and AVC. In the example above this doesn't always work because the numbers have been rounded to the nearest pound.

第七列显示平均成本（通常称为平均总成本）。这是总成本的平均值，因此我们将总成本除以产出 (Q)。您也可以通过添加 AFC 和 AVC 来解决。在上面的示例中，这并不总是有效，因为数字已四舍五入到最接近的磅数。

The final column shows marginal cost. As with marginal product, this can be calculated by finding the difference between the total cost of producing the given number of units and the total cost of producing one less unit of output.

For instance, to find the marginal cost of the fifth unit of output, you take the total cost of producing five units and subtract the total cost of producing four units. Algebraically: MC5 = TC5 − TC4 = 880 − 810 = 70.

最后一列显示边际成本。与边际产品一样，这可以通过找出生产给定数量单位的总成本与少生产一单位产出的总成本之间的差异来计算。例如，要找到第五个单位产出的边际成本，您可以用生产五个单位的总成本减去生产四个单位的总成本。代数：MC 5 = TC 5 - TC 4 = 880 - 810 = 70。

Now try and work out the answers to the table below. Click on the relevant sections in the table to reveal the answers. Remember that all the numbers should be rounded up or down to the nearest pound, so you might need a calculator.

现在试着找出下表的答案。单击表中的相关部分以显示答案。请记住，所有数字都应四舍五入到最接近的磅数，因此您可能需要一个计算器。

Here are the relevant curves. They have been plotted using the figures from the first table; not the one you have just filled in.

以下是相关曲线。它们是使用第一个表中的数字绘制的；不是你刚刚填写的那个。

Both diagrams have four lines on them; the three average curves and the marginal cost curve.

两张图都有四条线；三个平均曲线和边际成本曲线。

On the top one, the lines have been plotted from the figures in the initial cost table for the firm making computer laser printers. They look a bit odd, but there are some key points to pick up.

在顶部，线条是根据制造计算机激光打印机的公司的初始成本表中的数字绘制的。它们看起来有点奇怪，但有一些关键点需要了解。

First, the average fixed cost curve is continually falling, albeit at a slower rate towards the end. This makes sense, because a fixed number (in this case 500) is being divided by an ever-increasing number (i.e. output).

首先，平均固定成本曲线不断下降，尽管接近尾声的速度较慢。这是有道理的，因为固定数字（在本例中为 500）除以不断增加的数字（即输出）。

Secondly, the two average curves start fairly high, fall, and then rise again. This is due to the fact that initially the totals are being divided by very small numbers, giving large averages. The reason why the curves turn, will be explained shortly under 'How the cost curves are derived'

其次，两条平均曲线开始时相当高，然后下降，然后再次上升。这是因为最初将总数除以非常小的数字，得出较大的平均值。曲线转向的原因将在“成本曲线的推导方式”下稍后解释

Finally, and most importantly, the marginal cost curve cuts the average cost and average variable cost curves at their minimum points, where they are temporarily flat.

The reason for this is exactly the same as the reason why the marginal product curve cut the average product curve at the maximum.

It is worth going through this again to save you looking back at the last Learn-It, the explanation can be found just after the next diagram.

最后，也是最重要的一点，边际成本曲线在平均成本和平均可变成本曲线的最低点处截断，它们暂时平坦。其原因与边际产品曲线在最大值处切平均产品曲线的原因完全一样。值得再次阅读以节省您回顾上一个 Learn-It 的时间，可以在下一个图表之后找到解释。

The bottom diagram (of the two above) shows sketches of the four curves. Although you can see that they are not totally accurate, they do have the same characteristic as the actual curves, and they are much easier to deal with for analysis purposes, as you will see in the topic on 'Market structure'.

Notice that the MC still cuts the AC and AVC at their minimum and the AFC is continually downward sloping.

底部图（以上两个）显示了四条曲线的草图。尽管您可以看到它们并不完全准确，但它们确实具有与实际曲线相同的特征，并且它们更易于处理以进行分析，正如您将在“市场结构”主题中看到的那样。请注意，MC 仍然将 AC 和 AVC 削减到最小值，并且 AFC 不断向下倾斜。

This diagram shows the three 'total' curves. There are a couple of points to note here.

该图显示了三个“总”曲线。这里有几点需要注意。

First, the TFC curve is flat. This is to be expected because fixed costs remain constant.

首先，TFC 曲线是平坦的。这是意料之中的，因为固定成本保持不变。

Secondly, the TC and TVC curves are parallel. This is because the difference between the two is the fixed cost, which is constant. This means that every point on the TVC curve simply shifts up by 500.

其次，TC 和 TVC 曲线是平行的。这是因为两者之间的差异是固定成本，它是恒定的。这意味着 TVC 曲线上的每个点都会简单地向上移动 500。

Finally, the TC and TFC curve both start on the y-axis at 500, to represent the fixed cost. The TVC curve does not exist until Q = 1. Remember, there are no variable costs until something is actually produced!

最后，TC 和 TFC 曲线都在 y 轴上从 500 开始，表示固定成本。TVC 曲线在 Q = 1 之前不存在。请记住，在实际生产某些东西之前没有可变成本！