微观经济学svc的公式（国际课程ALevel经济重点内容）

The origins of the Phillips curve 菲利普斯曲线的由来

In 1958, an economist called Phillips published a paper stating that there was a trade off between the rate of change of money wages and unemployment rate. But it was not some brilliant theory that he had invented, he had simply collected data on wage inflation and unemployment for every year between 1861 and 1957, plotted a scatter diagram and drawna line of best fit.

1958年，一位叫菲利普斯的经济学家发表了一篇论文，指出货币工资的变化率和失业率之间存在着一种交易关系。但这并不是他发明的什么高明的理论，他只是收集了1861年至1957年期间每年的工资通胀和失业数据，绘制了一个散点图，并画出了一条最佳拟合线。

This might sound a bit useless, but when you think of how closely related the rate of change of money wages is to the rate of inflation, this relationship became very significant.

这听起来可能有点无用，但当你想到货币工资的变化率与通货膨胀率有多么密切的关系时，这种关系就变得非常重要。

The original data suggested that zero inflation was compatible with an unemployment rate of around 2.5%. If the government wanted to reduce unemployment below 2.5%, they could see the cost in terms of higher inflation and vice versa. Further research suggested that this relationship seemed to hold for most developed countries in the world.

最初的数据表明，零通货膨胀与2.5%左右的失业率是一致的。如果政府想把失业率降低到2.5%以下，他们可以看到通胀率上升的代价，反之亦然。进一步的研究表明，这种关系似乎适用于世界上大多数发达国家。

This was a godsend for the government. Although they could not control unemployment and inflation at the same time, they now had a 'guide' that told them exactly how much inflation to expect for a given reduction in unemployment. Equally, if inflation was high, they could see how much unemployment to expect for a given cut in the rate of inflation.

这对政府来说是个天赐良机。虽然他们不能同时控制失业和通货膨胀，但他们现在有了一个 "指南"，准确地告诉他们在减少失业的情况下可以预期多少通货膨胀。同样，如果通货膨胀率很高，他们可以看到在通货膨胀率降低的情况下，预期会有多少失业。

Why did the relationship hold? 为什么这种关系会成立？Why would a reduction in unemployment cause the inflation rate to rise? 为什么失业率的降低会导致通货膨胀率的上升？

If the government decided to cut unemployment through an expansionary fiscal or monetary policy, the resulting shift in the aggregate demand curve would increase output, which could only be accommodated by employing more labour. Money wages had to be raised to attract these new workers (who were voluntarily unemployed at the lower wage rate). This, in turn would cause an inflationary rise in the price level. So unemployment fell, but inflation rose.

如果政府决定通过扩张性的财政或货币政策来降低失业率，总需求曲线由此产生的变化将增加产出，这只能通过雇用更多的劳动力来解决。货币工资必须提高以吸引这些新工人（他们在较低的工资率下自愿失业）。这反过来又会导致价格水平的通胀上升。因此，失业率下降，但通货膨胀上升。

The breakdown of the original Phillips curve 原始菲利普斯曲线的崩溃

Most of the politicians, who took this relationship as gospel, did not appreciate fully one simple point. This 'Phillips curve' was not some theory that was cast in stone, like Newton's apples falling out of trees. It was simply a relationship between two variables that had held true for the past 100 years. Everyone hoped that the relationship would be true for the next 100 years, but that did not mean that it would.

大多数把这种关系当作福音的政客，并没有完全理解一个简单的问题。这个 "菲利普斯曲线 "并不是什么石破天惊的理论，就像牛顿的苹果从树上掉下来一样。它只是两个变量之间的关系，在过去的100年里一直保持不变。每个人都希望这种关系在未来的100年里都是真实的，但这并不意味着它会发生。

It fact, the relationship started to break down as early as the late 60s. Inflation and unemployment started rising together. What was going on? The relationship had worked for the past ten years, so there must have been some sort of short-term connection. Perhaps this relationship did not survive over a long period of time.

事实上，这种关系早在60年代末就开始崩溃了。通货膨胀和失业开始一起上升。发生了什么事？这种关系在过去的十年里是有效的，所以一定有某种短期的联系。也许这种关系并没有在很长一段时间内持续下去。

The expectations - augmented Phillips curve 预期--增强的菲利普斯曲线

An economist called Friedman tried to explain what was going on in the context of shifting short run Phillips curves and one vertical long run Phillips curve.

一位叫弗里德曼的经济学家试图解释在短期菲利普斯曲线变化和一个垂直的长期菲利普斯曲线的背景下发生了什么。

Exp. Inf. is short for Expected Inflation.

Exp. Inf. 是预期通货膨胀的简称。

In the diagram above, you can see three short run 'normal' looking Phillips curves and a green vertical long run Phillips curve. Let us assume that the economy begins at point A, with 0% inflation and a rate of unemployment of U*. The government decides that it wants unemployment to be lower. It increases aggregate demand by, say, building some new roads. In order to attract the required workers, the money wage is increased. Previously unemployed workers take the bait (frictionally, or structurally unemployed), unemployment falls to U1 at a cost of increasing inflation (3%). The economy moves from point A to point B along the short run Phillips curve SRPC1.

在上图中，你可以看到三条短期的 "正常 "菲利普斯曲线和一条绿色的垂直长期菲利普斯曲线。让我们假设经济开始于A点，通货膨胀率为0%，失业率为U*。政府决定要降低失业率。它增加了总需求，比如说修建一些新的道路。为了吸引所需的工人，货币工资被提高。以前失业的工人上钩（摩擦性失业，或结构性失业），失业率下降到U1，代价是通货膨胀率上升（3%）。经济沿着短期菲利普斯曲线SRPC1从A点移动到B点。

Notice that this curve has been labelled 'exp. inf. = 0%'. This means that workers expect future inflation to be 0%. They took the job with increased money wages expecting inflation to stay at 0% so that the real wage is higher. Workers only increase their supply of labour in response to an increase in real wages.

请注意，这条曲线被标为 "exp. inf. = 0%"。这意味着工人预期未来的通货膨胀率为0%。他们接受了增加货币工资的工作，期望通货膨胀率保持在0%，这样实际工资就会提高。工人只有在实际工资增加的情况下才会增加劳动的供给。

But, the increase in money wages forced the inflation rate up to 3%. The new workers did not realise this straight away. They initially suffer from money illusion. Before long the workers realise that they have, in a sense, been duped. Real wages have not increased at all. The new workers were not prepared to work at this lower real wage rate, so they withdraw their labour services and become unemployed again. The economy moves from point B to point C. Unemployment is back up to U*, but inflation stays where it is because money wages have not fallen back to their original level. The economy is now on a different short run Phillips curve (SRPC2) with expected inflation equal to 3%.

但是，货币工资的增加迫使通货膨胀率上升到3%。新工人并没有直接意识到这一点。他们最初受到货币幻觉的影响。不久，工人们就意识到，从某种意义上说，他们被愚弄了。实际工资根本没有增加。新工人不准备在这种较低的实际工资率下工作，所以他们撤回他们的劳动服务，再次成为失业者。经济从B点转到C点。失业率回到了U*，但通货膨胀率保持在原来的水平，因为货币工资并没有回落到原来的水平。现在经济处于不同的短期菲利普斯曲线（SRPC2）上，预期通货膨胀率等于3%。

If the government tries to reduce unemployment again, the same thing will happen. The economy will move from point C to D and then to E. In other words, every time the government tries to reduce unemployment below U*, it manages to do it in the short run, but as the workers suss out the money illusion, the economy goes back to the level of unemployment U*, but at a higher, and permanent, level of inflation. Hence, the long run Phillips curve is the green vertical line LRPC. Unemployment can be higher than U* in the long run, but not below U*.

如果政府试图再次降低失业率，同样的事情会发生。换句话说，每次政府试图将失业率降低到U*以下时，它都能在短期内做到这一点，但随着工人发现货币幻觉，经济又回到了失业率U*的水平，但通货膨胀的水平更高，而且是永久性的。因此，长期的菲利普斯曲线是绿色垂直线LRPC。在长期内，失业率可以高于U*，但不能低于U*。

The level of unemployment U* is often called the non-accelerating inflation rate of unemployment (NAIRU). Quite simply, at U*, inflation is non-accelerating. If unemployment is below U*, then inflation accelerates.

失业率U*的水平通常被称为非加速通胀失业率（NAIRU）。很简单，在U*，通货膨胀是不加速的。如果失业率低于U*，那么通货膨胀就会加速。

Once the government works out that reducing unemployment below U* in the long run is futile, it has to get inflation down to where it was before. It can do this, but only by getting workers' expectations of future inflation down to where they were before.

一旦政府发现，从长远来看，将失业率降低到U*以下是徒劳的，它必须将通货膨胀率降低到以前的水平。它可以做到这一点，但只有通过让工人对未来通货膨胀的预期下降到以前的水平。

If the economy is at point C, the only way that the government can reduce inflation back down to 0% and convince workers that this is permanent is to move down SRPC2 from point C to point F, and stay there for a while. This will be at a cost of much higher unemployment ("the price worth paying for lower inflation" - Norman Lamont, ex-Chancellor, especially after that comment!). In fact, the cost in terms of increased unemployment is higher than the benefit the government thought they would receive in terms of lower unemployment originally (i.e. U2 - U* > U* - U1). Once workers' expectations of future inflation are back down to 0%, then the government can reduce unemployment to U* without inflation rising again. The short run Phillips curve shifts from SRPC2 to SRPC1 and the economy moves from point F back to point A.

如果经济处于C点，政府能够将通货膨胀率降低到0%，并使工人相信这是永久性的，唯一的办法就是将SRPC2从C点移到F点，并在那里停留一段时间。这将以更高的失业率为代价（"为降低通货膨胀率而付出的代价是值得的"--诺曼-拉蒙特，前总理，特别是在这一评论之后！）。事实上，失业率上升的代价高于政府最初认为他们会得到的失业率下降的好处（即U2-U*>U*-U1）。一旦工人对未来通货膨胀的预期回落到0%，那么政府就可以将失业率降低到U*，而不会再出现通货膨胀。短期菲利普斯曲线从SRPC2转移到SRPC1，经济从F点回到A点。

The natural rate of unemployment 自然失业率

The implication of the above analysis is that there will always be some unemployment in an economy. This seems to be true looking back at past data. But who are these unemployed workers?

上述分析的含义是，一个经济体中总会有一些失业。回顾过去的数据，这似乎是真的。但这些失业的工人是谁呢？

The U* level of unemployment consists of all the frictionally and structurally unemployed. In a sense, they are all voluntarily unemployed. Frictionally unemployed workers could get a job at any time. They are simply taking their time and finding the best job. It may seem a bit harsh to say that those who are structurally unemployed do so voluntarily (remember our shipbuilder?), but most of them could actually find a job, but it might involve a life-wrenching move from the family home.

U*的失业水平包括所有的摩擦性失业和结构性失业。在某种意义上，他们都是自愿失业的。摩擦性失业的工人可以在任何时候找到工作。他们只是在慢慢寻找最好的工作。说那些结构性失业的人是自愿的似乎有点苛刻（还记得我们的造船师吗？），但他们中的大多数人实际上可以找到一份工作，但这可能涉及到从家庭住宅搬走的痛苦生活。

Given that there will always be some voluntary unemployment in an economy, this level of unemployment is often referred to as the natural rate of unemployment, because it occurs, in a sense, naturally. It occurs 'naturally' even when the economy is at its long run equilibrium.

鉴于一个经济体中总会有一些自愿的失业，这种失业水平通常被称为自然失业率，因为它在某种意义上是自然发生的。即使经济处于长期均衡状态，它也会 "自然 "发生。

In the diagram above, DL and SL are the usual labour demand and supply curves. Another supply curve is labelled 'workforce'. Remember that the workforce includes all those who are employed and unemployed but willing and able to work and looking for work. SL represents the supply of labour at the given real wage rate. Those who are structurally or frictionally unemployed may not want to work at the given wage. At real wage W1, therefore, L1 workers are employed and L2 - L1 workers are in the workforce, but decide not to supply their labour services for the given real wage rate W1. They are voluntarily unemployed. They represent the 'naturally' unemployed elements of the workforce.

在上图中，DL和SL是通常的劳动力需求和供给曲线。另一条供给曲线被标为 "劳动力"。请记住，劳动力包括所有就业和失业但愿意并能够工作和寻找工作的人。SL代表在给定的实际工资率下的劳动力供给。那些结构性或摩擦性失业的人可能不想在给定的工资下工作。因此，在实际工资W1下，L1的工人被雇用，L2-L1的工人在劳动力中，但决定不以给定的实际工资率W1提供他们的劳动服务。他们是自愿的失业者。他们代表了劳动力中 "自然 "失业的因素。

Finally, note that the two supply curves get closer together at higher wages. This is to be expected. At higher real wage rates, fewer workers will stay frictionally and structurally unemployed. They will be tempted by the higher real wage and enter employment.

最后，请注意，在工资较高的情况下，这两条供给曲线会越来越接近。这是可以预期的。在较高的实际工资率下，较少的工人会保持摩擦性和结构性的失业。他们会受到更高的实际工资的诱惑而进入就业。

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