A-level economics revision guides and question banks covering labour markets, supply and demand, market structure and all core economics a-level topics.
以下内容我们会持续更新：
今天带给大家Alevel经济笔记是：
总需求和总供给篇-Aggregate Supply
Aggregate supply is the aggregate of all the supply in the economy. Hence, the aggregate supply (from now on, AS) curve is the sum of all the industry supply curves. It shows the relationship between the price level and real output (or real national income).
总供给是经济中所有供给的总和。因此，总供给（从现在开始，AS）曲线是所有行业供给曲线的总和。它显示了价格水平与实际产出（或实际国民收入）之间的关系。
When we looked at firm and industry cost curves (see the 'Costs and revenues' topic and the relevant 'Market structure' topic) it was important to distinguish between the short and long run. We have to do this again here, in particular, the prices of all factor inputs (including wage rates) are assumed to be constant in the short run.
当我们查看公司和行业成本曲线时（参见“成本和收入”主题和相关的“市场结构”主题），区分短期和长期是很重要的。我们必须在这里再次这样做，特别是假设所有要素投入的价格（包括工资率）在短期内是恒定的。
It makes sense, therefore, that in the short run the AS curve will be upward sloping, just like the industry supply curves. The obvious reason is that all the industry supply curves that are added together are upward sloping too. There is a more technical explanation, though.
因此，在短期内 AS 曲线向上倾斜是有道理的，就像行业供给曲线一样。显而易见的原因是所有加在一起的行业供给曲线也是向上倾斜的。不过，还有一个更技术性的解释。
If real output is to increase in the short run, firms cannot attract new labour by increasing the wage rate.
The only way to make more output is to get the current workforce to work harder (overtime, perhaps).
In the real world, overtime pays double the wage rate, or maybe time and a half. So the costs to the firms and industries are likely to rise as real output rises.
These increased costs will tend to be passed onto the consumer through higher prices. In a roundabout way, the increase in real output has resulted in a rise in the price level.
如果要在短期内增加实际产出，企业就无法通过提高工资率来吸引新的劳动力。增加产出的唯一方法是让当前的劳动力更加努力地工作（也许是加班）。在现实世界中，加班费是工资的两倍，或者可能是一个半月时间。因此，随着实际产出的增加，企业和行业的成本可能会上升。这些增加的成本往往会通过更高的价格转嫁给消费者。以一种迂回的方式，实际产出的增加导致了价格水平的上升。
The short run AS curve shifts for similar reasons as a firm's, or an industry's supply curve might shift. Anything that causes the costs of the industries within the economy to change (regardless of changes in the price level) will shift the AS curve.
The factors must have nothing to do with changes in the general price level, remember. Otherwise, we would be dealing with a movement along the AS curve and not a shift in the curve.
短期 AS 曲线移动的原因与公司或行业的供给曲线可能移动的原因相似。任何导致经济中行业成本发生变化（无论价格水平如何变化）的因素都会使 AS 曲线移动。请记住，这些因素必须与一般价格水平的变化无关。否则，我们将处理沿AS 曲线的移动，而不是曲线的移动。
In the diagram you can see that the short run AS curve (or SRAS curve) has shifted upwards (or to the left) from SRAS1 to SRAS2. There are two different ways that this can be interpreted.
在图中，您可以看到短期 AS 曲线（或 SRAS 曲线）已从 SRAS 1向上（或向左）移动到 SRAS 2。有两种不同的解释方式。
You could argue that, for a given level of real output, Y1, the price level has risen due to a rise in the costs of various industries (like an increase in wage rates, other input prices or even the tax imposed by the government) from P1 to P2.
您可以争辩说，对于给定的实际产出水平 Y 1，由于各行业成本的上升（如工资率、其他投入价格甚至政府征收的税款的上升），价格水平已经上升) 从 P 1到 P 2。
Another way of looking at it is that real output falls for a given price level due to the increases in industries' costs. The firms may be unable to push the cost increases onto the consumer (for whatever reason) so real output cannot remain at Y1, and so it falls to Y2. The economy cannot make as much real output at the given price level if their costs rise.
另一种看待它的方式是，由于行业成本的增加，实际产出在给定的价格水平下下降。公司可能无法将成本增加推给消费者（无论出于何种原因），因此实际产出不能保持在 Y 1，因此它会下降到 Y 2。如果成本上升，经济就无法在给定的价格水平上产生尽可能多的实际产出。
Just like with AD curves, the SRAS curves can also shift to the right. Obviously, this would happen if there were an increase in costs for firms in the economy as a whole.
就像 AD 曲线一样，SRAS 曲线也可以向右移动。显然，如果整个经济中公司的成本增加，就会发生这种情况。
Given that we are assuming that factor input price should remain constant in the short run, the reasons given for the shifts in the SRAS curve do not make much sense. In the real world, industries and economies are often on the receiving end of supply side shocks.
There is nothing they can do about them and they affect the costs of the industries or economies. The quadrupling of the price of oil in the 70s is a good example.
The industries of the UK could do nothing about it, but it increased the costs of nearly all firms in all industries at the time, causing the SRAS curve to shift to the left.
鉴于我们假设要素投入价格在短期内应该保持不变，所以给出的价格 SRAS 曲线移动的原因没有多大意义。在现实世界中，行业和经济体往往处于供给侧冲击的接收端。他们对此无能为力，它们会影响行业或经济的成本。70年代油价翻两番就是一个很好的例子。英国的行业对此无能为力，但它增加了当时几乎所有行业的所有公司的成本，导致 SRAS 曲线向左移动。
Different economists have different views about the long run AS curve (LRAS curve). You have probably come across the differences between Monetarist (or classical) economists and Keynesian economists in your studies. The two sets of economists have different views about the shape of the LRAS curve.
不同的经济学家对长期 AS 曲线（LRAS 曲线）有不同的看法。您可能在研究中发现了货币主义（或古典）经济学家和凯恩斯主义经济学家之间的差异。两组经济学家对 LRAS 曲线的形状有不同的看法。
Classical economists believe strongly in the concepts of supply and demand in all markets. Whilst they are prepared to believe that markets might not be in equilibrium in the short run, they believe that all markets clear (i.e. supply equals demand) in the long run.
They also believe that if all markets are working efficiently and all resources are being used, then the economy must be at a point on their production possibility frontier (PPF).
In other words, the economy is making as much as it can, given its resources.
古典经济学家坚信所有市场的供求概念。虽然他们准备相信市场在短期内可能不会处于平衡状态，但他们相信从长远来看所有市场都是出清的（即供给等于需求）。他们还认为，如果所有市场都有效运作并且所有资源都在使用，那么经济必须处于其生产可能性边界 (PPF)上的某个点。换句话说，鉴于其资源，经济正在尽可能多地赚钱。
Classical economists think that the LRAS curve is vertical. There is absolutely no spare capacity in the economy.
The maximum real output is already being produced. In these circumstances, if there is an increase in AD (a shift from AD1 to AD2) for whatever reasons then all that will happen is the price level will rise (from P1 to P2). Demand increases, but there is no more output to buy, so the price of the various goods and services is bid up.
古典经济学家认为 LRAS 曲线是垂直的。经济中绝对没有闲置的产能。已经产生了最大的实际产出。在这种情况下，如果 AD 增加（从 AD 1到 AD 2的转变）无论出于何种原因，那么所发生的一切就是价格水平将上升（从 P 1到 P 2）。需求增加，但没有更多的产出可购买，因此各种商品和服务的价格上涨。
Note that the economy is in equilibrium where the AD curve cuts the AS curve (in this case, the LRAS curve). This occurs at point A initially, and then at point B after the shift in the AD curve from AD1 to AD2.\
请注意，经济处于平衡状态，AD 曲线与 AS 曲线相切（在本例中为什么 LRAS 曲线）。这最初发生在 A 点，然后在 AD 曲线从 AD 1移动到 AD 2之后发生在 B 点。
The Keynesian viewJohn Maynard Keynes (1883 - 1946) is probably the most famous economist of the twentieth century. Until the depression of the 1930s, all economists were effectively classical. Unemployment rose to astronomical levels during the depression (a very bad recession!). The classical economists, with their belief in supply and demand up their sleeves, said that the labour market would 'clear'. Unemployment was caused by excess supply of labour due to the wage rate (the price) being too high. Before long, the wage rate would fall as workers realised that the only way to get work was to take a lower wage. Of course, when this didn't happen after a number of years, they could not explain why.
约翰·梅纳德·凯恩斯（John Maynard Keynes，1883 - 1946）可能是二十世纪最著名的经济学家。在 1930 年代大萧条之前，所有经济学家实际上都是古典经济学家。在大萧条时期，失业率上升到天文数字（是一场非常严重的衰退！）。古典经济学家坚信供求关系，他们认为劳动力市场将“出清”。失业是由于工资率（价格）过高导致劳动力供应过剩造成的。不久之后，工资率就会下降，因为工人们意识到获得工资的唯一途径就是降低工资。当然，当这种情况在多年后没有发生时，他们无法解释原因。
Keynes was an economist who was always looking for answers to problems. He didn't care that every other economist in the world said that wages would fall and, with them, unemployment. As far as he was concerned, it wasn't happening, so the theory was wrong. He argued that an economy could find itself in a situation where unemployment was high and stuck at the high rate. In other words, the economy could find itself in an equilibrium (i.e. a state of rest) that was not the full employment equilibrium.
凯恩斯是一位一直在寻找问题答案的经济学家。他不在乎世界上所有其他经济学家都说工资会下降，随之而来的是失业。就他而言，这并没有发生，所以这个理论是错误的。他认为，一个经济体可能会发现自己处于失业率高企并停滞不前的境地。换句话说，经济可能会发现自己处于一个不是充分就业均衡的均衡（即静止状态）。
In the diagram above, the levels of real output between 0 and Y1 are ones where there is a lot of excess capacity.
There are many unused resources (unemployed labour, for example) and the economy is at a point well within its PPF (see the topic called 'Market failure' for details of the PPF).
This was the situation in the depression of the 30s.
Keynes' solution was simple. If there is excess supply, the solution is not to hope the wage (and other prices) fall, causing the supply of labour to be offered onto the market to fall.
Why not close the gap by increasing demand?
Consumers were too poor at the time to create this increase in AD, so, Keynes argued, it was up to the government to create this demand, through investment in roads, railways, hospitals, etc. Not only would this create jobs for the unemployed, but it would also improve the infrastructure of the economy.
在上图中，介于 0 和 Y 1之间的实际产出水平是产能过剩的水平。有许多未使用的资源（例如失业劳动力），经济处于其 PPF 范围内的某个点（有关 PPF 的详细信息，请参阅名为“市场失灵”的主题）。这就是 30 年代大萧条时期的情况。凯恩斯的解决方案很简单。如果供应过剩，解决办法是不要希望工资（和其他价格）下降，从而导致向市场提供的劳动力供应下降。为什么不通过增加需求来缩小差距？当时的消费者太穷了，无法创造 AD 的这种增长，因此，凯恩斯认为，应该由政府通过投资公路、铁路、医院等来创造这种需求。这不仅会为失业者创造就业机会，但它也将改善经济的基础设施。
Anyway, diagrammatically, you can see that, up to point A, the AD curve can shift to the right without the price level rising.
A large increase in real output with no rise in the price level. Also note that at every point where an AD curve cuts the LRAS curve is an equilibrium point.
Importantly (as Keynes said), these equilibrium levels of real output can occur at levels below the full employment level of real output (like the equilibrium at point C, price P1 and real output Y1).
无论如何，从图表上看，你可以看到，直到 A 点，AD 曲线可以向右移动，而且价格水平没有上升。实际产出大幅增加，而且价格水平没有上升。另请注意，AD 曲线与 LRAS 曲线相交的每个点都是一个平衡点。重要的是（正如凯恩斯所说），实际产出的这些均衡水平可能发生在实际产出的充分就业水平以下的水平（如 C 点的均衡，价格 P 1和实际产出 Y 1）。
The section of the LRAS curve between points A and B shows the levels of output where the economy is coming out of recession.
If AD continues to rise (a shift to AD2, say), real output will still rise, but the price level will also rise. In this situation, some industries will still be experiencing excess capacity, but others will be finding that they are getting close to full capacity. So some prices will not be rising, but others will be.
The price level, remember, is a measure of the average price level across the whole economy. So, in this situation, the price level will rise.
LRAS 曲线在 A 点和 B 点滴之间的部分显示了经济走出衰退时的产出水平。如果 AD 继续上升（例如转向 AD 2），实际产出仍会上升，但价格水平也会上升。在这种情况下，一些行业仍会出现产能过剩，但其他行业会发现他们正接近满负荷生产。所以有些价格不会上涨，但有些价格会上涨。请记住，价格水平是衡量整个经济体平均价格水平的指标。所以，在这种情况下，价格水平会上涨。
The final section of the LRAS curve, above point B, is vertical. Keynes agreed with the classical economists that, once the economy had reached the full employment level of real output, any rise in AD will be inflationary.
A shift in AD from AD3 to AD4 will result in no increase in real output, but the price level will rise from P3 to P4. This last bit of the Keynesian LRAS curve is the same as the whole of the classical LRAS curve.
LRAS 曲线的最后一段，在 B 点上方，是垂直的。凯恩斯同意古典经济学家的观点，一旦经济达到实际产出的充分就业水平，AD 的任何上升都会引起通货膨胀。AD 从 AD 3到 AD 4的转变不会导致实际产出增加，但价格水平将从 P 3上升到 P 4。凯恩斯 LRAS 曲线的最后一点与整个经典 LRAS 曲线相同。
For those of you who prefer the 45 degree diagram analysis, look at the diagram below and see how it compares with the AS/AD diagram above.
对于那些喜欢 45 多图分析的人，请看下图，看看它与上面的 AS/AD 图得比较。
The Y = AD line at 45 degrees to the horizontal gives all the points where the economy is in equilibrium, just like all the points where the various AD curves cut the LRAS curve are equilibrium points in the previous diagram. Notice that each AD line in this diagram denotes planned expenditure, which is C I G X − M.
与水平成 45 度的 Y = AD 线给出了经济处于平衡状态的所有点，就像上图中各种 AD 曲线与 LRAS 曲线相切的所有点都是平衡点一样。请注意，此图中的每条 AD 线表示计划支出，即 C I G X - M。
Note that AD3 gives the full employment level of real national income (YFE), just as the AD curve, AD3, does as is crosses the LRAS curve at point B in the previous diagram.
请注意，AD 3给出了实际国民收入的充分就业水平（Y FE），正如 AD 曲线 AD 3在上图中的 B 点与 LRAS 曲线相交一样。
The AD4 lines are showing the same thing as well. In the first diagram you see the price rise to P4, and in the second diagram this rise in the price level is illustrated by the inflationary gap in green.
AD 4行也显示相同的内容。在第一张图中，您看到价格上涨到 P 4，而在第二张图中，价格水平的上涨通过绿色通胀缺口来说明。
The AD1 lines are also showing the same thing. In the first diagram, this gives a level of real output of Y1, which is below the full employment level, and in the second diagram it does the same. The deflationary gap in blue illustrates the downward pressure on prices of being in this recessionary position.
AD 1行也显示相同的内容。在第一个图中，这给出了一个实际产出水平 Y 1，低于充分就业水平，在第二个图中它也是如此。蓝色的通缩缺口表明处于这种衰退状态的价格面临下行压力。
You can probably see why examiners prefer the AS/AD approach. It shows both the Keynesian position and the classical position (when the LRAS curve is vertical), whereas the 45-degree diagram is just a Keynesian diagram.
Also, when AD shifts to a position past AD3, real output remains at the full employment level YFE. This doesn't really happen on the 45-degree diagram.
The AS/AD diagram also shows the price levels. The 45-degree diagram hints at what is going on with prices with its deflationary and inflationary gap, but it is not specific.
您可能会明白为什么审查员更喜欢 AS/AD 方法。它显示了凯恩斯位置和经典位置（当 LRAS 曲线垂直时），而 45 度图只是凯恩斯图。此外，当 AD 移动到超过 AD 3的位置时，实际产出保持在充分就业水平 Y FE。这在 45 度图上并没有真正发生。AS/AD 图还显示了价格水平。45 度图暗示了价格与通货紧缩和通胀差距的情况，但并不具体。
今天的Alevel经济笔记就更新到这里，如果大家对Alevel经济学感兴趣可以关注我们，
之前更新：
1、Alevel经济学习笔记：总需求和总供给篇-The Circular Flow of Income
2、Alevel经济学习笔记：总需求和总供给篇-The '45 Degree' Diagram
3、Alevel经济学习笔记：总需求和总供给篇-Aggregate Demand
后续我们还会更新我以下版块的内容~
