System.Xml.XmlElement

I have a Google Doc with a long list of posts I’ve been meaning to write.

我有一个谷歌文档，里面有一长串我一直想写的帖子。

Far down the list was a line that read “New Keynesian macroeconomics deserves a Nobel”.

名单的最下方有一行字：“新凯恩斯主义宏观经济学值得获得诺贝尔奖”。

Somehow I never got around to writing that post, and now I never will.

不知何故，我一直没有时间写那篇文章，现在我也永远不会了。

Because today, it happened!

因为今天，这件事发生了！

This year’s Econ Nobel went to Bob Hall and Mike Woodford, two of the theory’s most important creators.

今年的诺贝尔经济学奖授予了鲍勃·霍尔和迈克·伍德福德，他们是该理论最重要的两位创始人。

First, let me say that this prize is long overdue.

首先，我要说的是，这个奖项姗姗来迟。

In 2009, I asked my PhD advisor, Miles Kimball, who was the greatest living macroeconomist.

2009 年，我询问了我的博士生导师迈尔斯·金博尔 (Miles Kimball)，他是当今最伟大的宏观经济学家。

Without hesitation, he answered “Bob Hall”, and said he would be very surprised if Hall didn’t win the Nobel at some point.

他毫不犹豫地回答“鲍勃·霍尔”，并表示如果霍尔在某个时候没有获得诺贝尔奖，他会感到非常惊讶。

Hall’s work is breathtakingly broad; if you want good summaries, I recommend Alex Tabarrok and Tyler Cowen (as usual).

霍尔的工作范围极其广泛。如果你想要好的总结，我推荐 Alex Tabarrok 和 Tyler Cowen（像往常一样）。

As for Michael Woodford, everyone I know assumed that if New Keynesian macro ever did get the prize, Woodford would be included, as he literally wrote the book on it .

至于迈克尔·伍德福德，我认识的每个人都认为，如果新凯恩斯主义宏观确实获奖，伍德福德就会被包括在内，因为他确实写了这本书。

1

1

But anyway, let’s talk about New Keynesian economics — what it is, how it came about, why it’s important, and why it didn’t get a Nobel until now.

但无论如何，我们来谈谈新凯恩斯主义经济学——它是什么，它是如何产生的，为什么它很重要，以及为什么它直到现在才获得诺贝尔奖。

Let’s start with a brief history of modern macroeconomics.

让我们从现代宏观经济学的简史开始。

Back in the 1960s and early 1970s, most economists tried to understand the macroeconomy by looking at relationships between macroeconomic aggregates.

早在 20 世纪 60 年代和 70 年代初，大多数经济学家试图通过观察宏观经济总量之间的关系来理解宏观经济。

For example, “If income goes up by 10%, how much will spending go up?”.

例如，“如果收入增加 10%，支出会增加多少？”。

Or “If inflation goes up by 3 percentage points, how much will unemployment go down?”.

或者“如果通货膨胀上升3个百分点，失业率会下降多少？”。

2

2

The problem with that is that correlation isn’t causation .

问题在于相关性并不是因果关系。

Suppose you see that when inflation rises, unemployment goes down.

假设您看到当通货膨胀上升时，失业率下降。

That correlation is called a Phillips Curve.

这种相关性称为菲利普斯曲线。

So you think “OK, if we raise inflation, more people will get jobs”.

所以你会想“好吧，如果我们提高通货膨胀，更多的人就会找到工作”。

But you try that, and it doesn’t work — you push inflation up (by printing more money), but unemployment stays high.

但你尝试这样做，却行不通——你推高了通货膨胀（通过印更多的钱），但失业率仍然很高。

The correlation you saw before has now broken down.

您之前看到的相关性现在已经打破。

Now you’ve got two problems instead of one!

现在你遇到了两个问题，而不是一个！

This is a very simplified version of what a lot of economists think happened in the 1970s .

这是许多经济学家所认为的 20 世纪 70 年代发生的事情的一个非常简化的版本。

Whether that’s what really happened is a story for another day.

这是否真的发生了，那就是另一天的故事了。

But the stagflation of the 1970s prompted the econ profession as a whole to rethink how it modeled the macroeconomy.

但 20 世纪 70 年代的滞胀促使整个经济学界重新思考如何建模宏观经济。

A lot of researchers asked: What parts of the macroeconomy are invariant to policy?

许多研究人员问：宏观经济的哪些部分不受政策影响？

What are the solid foundations we can stand on, so that when we try to make some sort of change, we don’t cause our own theories to crumble?

我们可以立足哪些坚实的基础，以便当我们尝试做出某种改变时，不会导致我们自己的理论崩溃？

The answer most economists settled on was called “microfoundations”.

大多数经济学家给出的答案被称为“微观基础”。

They reasoned that the basic drivers of individual and corporate economic behavior shouldn’t change when macro policies like interest rates and government spending change.

他们认为，当利率和政府支出等宏观政策发生变化时，个人和企业经济行为的基本驱动因素不应改变。

Most importantly, those drivers include:

最重要的是，这些驱动因素包括：

Do all three of these really stay the same when economic policy changes?

当经济政策发生变化时，这三者真的保持不变吗？

Probably not completely.

可能不完全。

But it gave macroeconomists a place to start.

但它为宏观经济学家提供了一个起点。

So in the late 1970s and early 1980s, economists started to build macro models based on theories of individual and corporate behavior.

因此，在 20 世纪 70 年代末和 80 年代初，经济学家开始建立基于个人和企业行为理论的宏观模型。

These were called “microfounded” macro models.

这些被称为“微观基础”宏观模型。

The last of those three “microfoundations” — expectations — was particularly thorny to think about.

这三个“微观基础”中的最后一个——期望——尤其难以思考。

Almost any sort of expectation-formation process that you write down allows policymakers to trick people over and over, by surprising them systematically.

几乎任何一种你写下的预期形成过程都可以让政策制定者通过系统性地给人们带来惊喜来一次又一次地欺骗人们。

Economists thought that eventually , people should wise up to the government’s tricks.

经济学家认为，最终，人们应该识破政府的诡计。

So they came up with the idea that consumers and businesses should, on average, be as smart as the economists making the models.

因此，他们提出了这样的想法：平均而言，消费者和企业应该像制作模型的经济学家一样聪明。

If economists write down a model of how the world works, that model should be the average person’s mental model in the model .

如果经济学家写下一个世界如何运转的模型，那么这个模型应该是模型中普通人的心智模型。

Basically, people generally know how the economy works, and they plan accordingly.

基本上，人们普遍知道经济是如何运作的，并做出相应的计划。

In 1978, Bob Hall wrote a very influential paper that convinced a lot of economists that this was the right track.

1978 年，鲍勃·霍尔 (Bob Hall) 写了一篇非常有影响力的论文，使许多经济学家相信这是一条正确的道路。

Hall wanted to test a simple idea, originally developed by Milton Friedman: If people plan out their consumption in advance, then changes in the level of consumption should be completely random .

霍尔想测试一个最初由米尔顿·弗里德曼提出的简单想法：如果人们提前计划好他们的消费，那么消费水平的变化应该是完全随机的。

3 Nothing from last quarter should be able to predict the change in consumption this quarter — because if something last quarter mattered for this quarter’s consumption, people would already have changed their consumption last quarter!

3 上个季度的任何数据都不能预测本季度的消费变化——因为如果上个季度的某些事情对本季度的消费很重要，那么人们在上个季度就已经改变了他们的消费！

Hall found that, sure enough, a bunch of variables that seemed like they should be important for consumption — especially last quarter’s income — didn’t actually help predict changes in consumption.

霍尔发现，果然，一堆看似对消费很重要的变量——尤其是上季度的收入——实际上并不能帮助预测消费的变化。

At first blush, this might not seem like an important result.

乍一看，这似乎不是一个重要的结果。

After all, absence of evidence isn’t evidence of absence — there might be other variables that do predict changes in consumption, that Hall simply forgot to test.

毕竟，缺乏证据并不是不存在的证据——可能还有其他变量确实可以预测消费的变化，但霍尔只是忘记了测试。

And in fact, Hall did find one variable that predicted future changes in consumption: stock prices.

事实上，霍尔确实发现了一个可以预测未来消费变化的变量：股票价格。

So even in the formal sense, the basic theory didn’t quite hold.

因此，即使在形式意义上，基本理论也不太成立。

Nor did Hall’s result rule out the traditional Keynesian idea of consumption — if government spending surprises people, it can move consumption immediately, without creating any sort of predictable future change.

霍尔的结果也不排除传统凯恩斯主义的消费理念——如果政府支出让人们感到惊讶，它可以立即推动消费，而不会造成任何可预测的未来变化。

But it was an important result, for two reasons.

但这是一个重要的结果，原因有两个。

First, if people plan ahead when making their economic decisions, it should be possible for policymakers to influence today’s behavior by making promises about what they’ll do in the future .

首先，如果人们在做出经济决策时提前计划，那么政策制定者应该有可能通过对未来的行动做出承诺来影响今天的行为。

Second, if it’s impossible for economists to predict changes in consumption, that implies that consumers are as good at planning their future consumption as economists are.

其次，如果经济学家不可能预测消费的变化，那就意味着消费者和经济学家一样善于规划未来的消费。

If that’s true, it’s an important lesson for policy: If you want to make people consume more, or if you want to make businesses hire more, etc., you have to do it in a way such that people generally understand what you’re doing .

如果这是真的，这对政策来说是一个重要的教训：如果你想让人们消费更多，或者如果你想让企业雇用更多员工等等，你必须以一种让人们普遍理解你在做什么的方式来做。

So macroeconomists set out to make models of the economy in which people understand how the economy works.

因此，宏观经济学家开始建立经济模型，让人们了解经济如何运作。

At first, this effort didn’t go well.

起初，这项努力并不顺利。

For example, one very popular early idea — which eventually won a Nobel — was called “real business cycle” (RBC) theory.

例如，一个非常流行的早期想法 - 最终赢得了诺贝尔奖 - 被称为“真实商业周期”（RBC）理论。

This was the idea that recessions and booms are driven purely by changes in the rate of technological progress — if engineers happen to invent less useful stuff this quarter, you get a recession.

这种观点认为，衰退和繁荣纯粹是由技术进步速度的变化驱动的——如果工程师本季度碰巧发明了不太有用的东西，就会陷入衰退。

No one denies that technological inventions can be very important for economic growth — just look at how the AI boom is powering the U.S. economy right now .

没有人否认技术发明对经济增长非常重要——只要看看人工智能热潮目前如何为美国经济提供动力即可。

But the idea that tech progress drives the business cycle in a simple, mechanical way just doesn’t fit the evidence .

但技术进步以简单、机械的方式推动商业周期的想法并不符合证据。

In particular, productivity booms don’t seem to line up with economic booms , as RBC theory would predict.

特别是，正如加拿大皇家银行理论所预测的那样，生产率的繁荣似乎与经济繁荣并不相符。

4

4

Even more importantly, RBC models predict that monetary policy — raising and lowering interest rates — shouldn’t affect the real economy.

更重要的是，加拿大皇家银行的模型预测货币政策（提高和降低利率）不应影响实体经济。

Ed Prescott, the creator of RBC theory, famously declared that monetary policy “is as effective in bringing prosperity as rain dancing is in bringing rain.” But our best evidence says that Prescott was wrong — monetary policy almost certainly does affect the real economy .

加拿大皇家银行理论的创始人埃德·普雷斯科特（Ed Prescott）曾说过一句著名的话：货币政策“带来繁荣的效果就像祈雨舞带来降雨一样有效”。但我们最好的证据表明普雷斯科特是错误的——货币政策几乎肯定会影响实体经济。

So something’s going on there.

所以那里发生了一些事情。

Macroeconomists were missing something big — they didn’t understand how or why monetary policy boosts growth and employment.

宏观经济学家错过了一件大事——他们不明白货币政策如何或为何促进增长和就业。

During the 1990s, a bunch of economists started coming up with possible reasons why having the Fed buy bonds could result in more people getting jobs.

20 世纪 90 年代，一群经济学家开始提出让美联储购买债券可以让更多人找到工作的可能原因。

These ideas generally fell under the name of “New Keynesianism”.

这些思想通常被称为“新凯恩斯主义”。

As John Cochrane and others have pointed out, this was something of a misnomer.

正如约翰·科克伦 (John Cochrane) 和其他人指出的那样，这种说法有些用词不当。

Whereas John Maynard Keynes and his successors thought a lot about fiscal policy — i.e. government spending and taxes — the New Keynesians of the 1990s and 2000s focused almost entirely on monetary policy.

约翰·梅纳德·凯恩斯 (John Maynard Keynes) 及其继任者对财政政策（即政府支出和税收）思考了很多，而 20 世纪 90 年代和 2000 年代的新凯恩斯主义者几乎完全关注货币政策。

New Keynesian macro initially owed a lot more to Milton Friedman than it did to Keynes — everything was about the Fed, and the idea of fiscal stimulus initially fell by the wayside.

新凯恩斯主义宏观政策最初更多地归功于米尔顿·弗里德曼（Milton Friedman），而不是凯恩斯——一切都与美联储有关，而财政刺激的想法最初被搁置了。

Anyway, in the 90s and 2000s there were plenty of ideas about how monetary policy could affect the real economy.

不管怎样，在 20 世纪 90 年代和 2000 年代，关于货币政策如何影响实体经济有很多想法。

This is probably one big reason why New Keynesian economics was so slow to win a Nobel — it has so many creators that it’s not even clear who deserves the prize.

这可能是新凯恩斯主义经济学获得诺贝尔奖如此缓慢的一个重要原因——它的创造者如此之多，以至于甚至不清楚谁应该获奖。

Greg Mankiw, David Romer, Stanley Fischer, George Akerlof, Janet Yellen, Olivier Blanchard, Nobuhiro Kiyotaki, Jordi Gali, Mark Gertler, John Taylor, Guillermo Calvo, and a bunch of others contributed pieces to the edifice .

格雷格·曼昆、大卫·罗默、斯坦利·费舍尔、乔治·阿克洛夫、珍妮特·耶伦、奥利维尔·布兰查德、清泷信弘、乔迪·加利、马克·格特勒、约翰·泰勒、吉列尔莫·卡尔沃和其他一些人为这座大厦贡献了作品。

Most of these contributions were ideas about why prices are slow to adjust to macroeconomic fluctuations.

这些贡献大多是关于为什么价格对宏观经济波动调整缓慢的想法。

Basically, if you have something that decreases aggregate demand — say the Fed raises interest rates like in 1980, or there’s a banking panic after a housing bubble bursts like in 2008 — there’s a question of why companies don’t just cut prices and maintain the same level of output.

基本上，如果有某种因素降低了总需求——比如美联储像 1980 年那样提高利率，或者像 2008 年那样在房地产泡沫破裂后出现银行业恐慌——那么就会出现一个问题，为什么企业不直接降价并维持相同的产出水平。

If there’s something causing prices to fall too slowly , that can force companies to produce less instead.

如果有什么原因导致价格下降太慢，就会迫使企业减少产量。

A lot of New Keynesian theory is about why companies have difficulty cutting prices.

许多新凯恩斯主义理论都是关于为什么公司难以降价。

Bob Hall made very important contributions here too!

鲍勃·霍尔在这里也做出了非常重要的贡献！

The basic New Keynesian model explains how interest rates can affect GDP, but it doesn’t explain why that affects employment .

基本的新凯恩斯主义模型解释了利率如何影响GDP，但没有解释为什么会影响就业。

After all, if growth slows down, it’s not immediately obvious why a bunch of people should be thrown out of their jobs.

毕竟，如果增长放缓，那么为什么要解雇一群人并不是显而易见的。

In a 2005 paper , Hall made a model explaining how wages might be slow to adjust to changes in demand — meaning that when there’s a downturn, companies can’t just cut wages, but instead have to lay off workers.

在 2005 年的一篇论文中，霍尔提出了一个模型，解释了工资如何缓慢地适应需求变化——这意味着当经济低迷时，公司不能只是削减工资，而是必须解雇工人。

5

5

Anyway, New Keynesian economics wasn’t the brainchild of a few famous founders — it was a riot of new ideas.

无论如何，新凯恩斯主义经济学并不是少数著名创始人的创意——它是新思想的狂欢。

It needed someone to come synthesize all of those ideas into something simple that central bankers could use to set monetary policy in real life.

它需要有人将所有这些想法综合成简单的东西，以便中央银行家可以用来制定现实生活中的货币政策。

That man was Mike Woodford.

那个人就是迈克·伍德福德。

In a paper with the late Julio Rotemberg , Woodford laid out a simple New Keynesian model.

在与已故胡里奥·罗腾伯格合作的一篇论文中，伍德福德提出了一个简单的新凯恩斯主义模型。

On the question of why companies have difficulty cutting prices in a recession, he punted — Woodford simply assumed that for whatever reason, only some companies are able to change their prices each quarter.

关于为什么公司在经济衰退期间难以降价的问题，他提出了质疑——伍德福德只是简单地假设，无论出于何种原因，只有一些公司能够每个季度改变价格。

6 (This idea is called “Calvo pricing”, after its creator, Guillermo Calvo.) The rest of the model is pretty simple.

6（这个想法被称为“Calvo 定价”，以其创始人 Guillermo Calvo 的名字命名。）模型的其余部分非常简单。

Woodford uses the same basic consumption-smoothing model from Hall’s 1978 paper, in which people’s decision of how much to consume and how much to save depends on the interest rate.

伍德福德使用了霍尔 1978 年论文中相同的基本消费平滑模型，其中人们决定消费多少和储蓄多少取决于利率。

He assumes that the central bank (i.e., the Fed) sets interest rates according to a simple rule that balances out the risks of inflation and unemployment.

他假设中央银行（即美联储）根据平衡通货膨胀和失业风险的简单规则来设定利率。

There are a few more assumptions in there, but those are the basics.

其中还有一些假设，但这些是基础知识。

This simple model provides a guide for monetary policy.

这个简单的模型为货币政策提供了指导。

It explains how the central bank can cause a recession in the short term — like Paul Volcker did in the early 1980s, when he raised interest rates to fight inflation — but can’t raise employment forever by keeping rates permanently low.

它解释了央行如何在短期内造成经济衰退——就像保罗·沃尔克在 20 世纪 80 年代初所做的那样，当时他提高利率以对抗通货膨胀——但无法通过永久保持低利率来永远提高就业。

And it explains how the central bank can respond to a drop in private demand — say, from a financial crisis like the one in 2008 — by cutting interest rates to stabilize the economy in the short term.

它还解释了央行如何通过降息以在短期内稳定经济来应对私人需求下降（例如 2008 年金融危机造成的需求下降）。

In other words, Woodford’s model — which he later expanded into a famous book — is a grand synthesis of the general consensus that emerged from the intellectual ferment of macroeconomics from the 1970s through the 2000s.

换句话说，伍德福德的模型——后来他将其扩展为一本著名的书——是对 20 世纪 70 年代到 2000 年代宏观经济学知识骚动中出现的普遍共识的综合。

We knew that aggregate demand was a real thing.

我们知道总需求是真实存在的。

We knew that the economy had trouble adjusting to negative demand shocks, resulting in a lot of disruption — reduced output, people getting thrown out of work, and so on.

我们知道经济难以适应负面的需求冲击，从而导致了很多破坏——产出减少、人们失业等等。

And we knew that monetary policy could boost the economy in the short term, but that its effect probably faded in the long term.

我们知道货币政策可以在短期内提振经济，但从长期来看其效果可能会减弱。

Woodford gave us the simplest plausible model to describe all of that, and to offer central banks a badly-needed road map for stabilizing the economy.

伍德福德为我们提供了最简单、合理的模型来描述所有这一切，并为央行提供了急需的稳定经济的路线图。

Because it was so simple and so applicable, Woodford’s New Keynesian model became the standard tool of central banks around the world.

由于伍德福德的新凯恩斯主义模型如此简单且如此适用，它成为世界各国央行的标准工具。

No sooner was his synthesis complete, however, than it ran into a huge problem.

然而，他的合成刚完成，就遇到了一个大问题。

In 2008 and 2009, the U.S. and European economies were hit by such a huge negative demand shock that cutting interest rates all the way to zero failed to put things right.

2008年和2009年，美国和欧洲经济受到巨大的负面需求冲击，利率一路降到零也未能扭转局面。

Something else was needed.

还需要其他东西。

There were three basic ideas for what that “something else” should be.

对于“其他东西”应该是什么，存在三个基本想法。

The first is contained in Woodford’s model, and draws on the basic idea in Hall’s papers.

第一个包含在伍德福德的模型中，并借鉴了霍尔论文中的基本思想。

It’s the idea of “forward guidance” .

这就是“前瞻指导”的想法。

If the central bank can promise to leave interest rates low for a long time even after the recession is over, that can prompt consumers to spend more today — thus hastening the end of the recession.

如果央行能够承诺即使在经济衰退结束后仍将长期保持低利率，这可能会促使消费者今天增加支出，从而加速经济衰退的结束。

7 The second is quantitative easing — having the Fed buy long-term bonds instead of just short-term ones, in order to push down long-term interest rates.

7 第二个是量化宽松——让美联储购买长期债券而不仅仅是短期债券，以压低长期利率。

QE isn’t in Woodford’s model, but he eventually came around to supporting it .

量化宽松并不属于伍德福德的模式，但他最终转而支持量化宽松。

The third idea was fiscal stimulus .

第三个想法是财政刺激。

If interest rates go all the way to zero, then government spending can become a more effective way of raising demand (as long as the central bank doesn’t cancel out the stimulus by raising rates again).

如果利率一路降至零，那么政府支出可能成为提高需求的更有效方式（只要央行不再次加息来抵消刺激措施）。

When the Great Recession hit, New Keynesian economists scrambled to put Keynes back into their theories, by adding a role for fiscal stimulus.

当大衰退袭来时，新凯恩斯主义经济学家争先恐后地将凯恩斯主义重新纳入他们的理论中，增加了财政刺激的作用。

[T]he multiplier linking government purchases to GDP may be in the range of 0.7 to 1.0…but higher values are not ruled out.

将政府采购与 GDP 挂钩的乘数可能在 0.7 到 1.0 的范围内……但不排除更高的值。

New Keynesian macro models have multipliers in that range as well…Multipliers are higher—perhaps around 1.7—when the nominal interest rate is at its lower bound of zero, as it was during 2009.

新凯恩斯主义宏观模型的乘数也在这个范围内……当名义利率处于零下限时（如 2009 年那样），乘数会更高（可能在 1.7 左右）。

In that paper, Hall explains how fiscal stimulus can be effective even in light of his famous result from 1978.

在那篇论文中，霍尔解释了财政刺激如何能够发挥作用，即使考虑到他 1978 年的著名结果。

Even if there is no simple “consumption function” linking stimulus directly to spending, there are plenty of ways that stimulus can affect the behavior of companies and consumers, especially when interest rates are at zero.

即使不存在将刺激措施与支出直接联系起来的简单“消费函数”，刺激措施也可以通过多种方式影响企业和消费者的行为，尤其是在利率为零的情况下。

And Woodford wrote a paper in 2011 showing how stimulus works in his basic model:

伍德福德在 2011 年写了一篇论文，展示了刺激措施在他的基本模型中如何发挥作用：

This paper explains the key factors that determine the output multiplier of government purchases in New Keynesian models, through a series of simple examples that can be solved analytically.

本文通过一系列可解析求解的简单例子，解释了新凯恩斯主义模型中决定政府购买产出乘数的关键因素。

Sticky prices or wages allow for larger multipliers than in a neoclassical model, though the size of the multiplier depends crucially on the monetary policy response.

粘性价格或工资允许比新古典模型更大的乘数，尽管乘数的大小主要取决于货币政策的反应。

A multiplier well in excess of one is possible when monetary policy is constrained by the zero lower bound, and in this case welfare increases if government purchases expand to partially fill the output gap that arises from the inability to lower interest rates.

当货币政策受到零下限的限制时，乘数可能远远超过一，在这种情况下，如果政府扩大购买以部分填补因无法降低利率而产生的产出缺口，福利就会增加。

So in the end, the New Keynesians went beyond the ideas of Milton Friedman, and brought some Keynes back into their theories.

所以最终，新凯恩斯主义者超越了米尔顿·弗里德曼的思想，并将一些凯恩斯主义带回了他们的理论中。

But New Keynesianism’s biggest success arguably came not in the Great Recession, but in the post-pandemic inflation of 2021-23.

但新凯恩斯主义最大的成功可以说不是来自大衰退，而是来自 2021-23 年大流行后的通货膨胀。

Inflation spiked to 9% in 2022, but then came down to around 3% in early 2023 after the Fed raised interest rates.

2022 年通货膨胀率飙升至 9%，但在美联储加息后于 2023 年初降至 3% 左右。

But what’s remarkable is that unlike in the early 1980s, this happened without a big rise in unemployment!

但值得注意的是，与 20 世纪 80 年代初不同的是，这一切发生时失业率并没有大幅上升！

It’s not clear exactly why this happened , of course, but it sure looks like a big victory for the kind of New Keynesian macro that Bob Hall and Mike Woodford pioneered.

当然，目前还不清楚为什么会发生这种情况，但这看起来确实是鲍勃·霍尔和迈克·伍德福德开创的新凯恩斯主义宏观经济的重大胜利。

The most likely explanation for this “immaculate disinflation” is that as soon as businesses realized that the Fed would do whatever it took to beat inflation, they stopped raising prices — and inflation simply ended.

对于这种“完美的通货紧缩”最可能的解释是，一旦企业意识到美联储将不惜一切代价击败通胀，他们就停止提高价格——通胀就这样结束了。

It didn’t require demand destruction like Volcker caused in the early 1980s.

它不需要像 20 世纪 80 年代初沃尔克那样破坏需求。

It didn’t require legions of down-and-out unemployed blue-collar workers cutting back on essential purchases to finally force companies to stop raising their prices.

它并不需要大批穷困潦倒的失业蓝领工人削减必需品的采购来最终迫使公司停止提高价格。

All it required was a clear Fed commitment, and forward-looking expectations — exactly the mechanisms at the core of Bob Hall and Mike Woodford’s models.

它所需要的只是美联储的明确承诺和前瞻性预期——这正是鲍勃·霍尔和迈克·伍德福德模型的核心机制。

It was this episode, even more than 2008-9, that truly represented New Keynesianism’s acid test.

正是这一事件，甚至比2008年9月更真正代表了新凯恩斯主义的严峻考验。

And it seems to have passed with flying colors.

它似乎已经顺利通过了。

There was always a question mark hanging over the theory — it was always unclear whether it could shape the future instead of simply telling a story about the past.

这个理论始终存在一个问号——人们始终不清楚它是否能够塑造未来，而不是简单地讲述过去的故事。

Since 2022-23, the answer to that question looks like a much more unambiguous “yes”.

自 2022-23 年以来，这个问题的答案看起来更加明确“是”。

I wouldn’t be surprised if that had something to do with this long-overdue Nobel.

如果这与这个姗姗来迟的诺贝尔奖有关，我不会感到惊讶。

These are simple examples, but sometimes these models could get very big and complicated!

这些都是简单的例子，但有时这些模型可能会变得非常庞大和复杂！

This was far from Hall’s only contribution to New Keynesian macro.

这远不是霍尔对新凯恩斯主义宏观的唯一贡献。

Another example is his 1986 paper showing how monopoly power could exacerbate economic booms and busts.

另一个例子是他 1986 年发表的论文，展示了垄断权力如何加剧经济繁荣和萧条。

Woodford separately wrote down a model of how Calvo pricing might arise from imperfect information.

伍德福德单独写下了一个模型，说明卡尔沃定价如何从不完美的信息中产生。

It’s not clear how important this model is, though, or whether Woodford — or anyone else — actually thinks that this is the real reason prices are slow to adjust.

不过，目前尚不清楚这种模式有多重要，也不清楚伍德福德或其他任何人是否真的认为这是价格调整缓慢的真正原因。

Interestingly, it looks like we did this.

有趣的是，我们似乎做到了这一点。

The Fed kept interest rates ultra-low even in the late 2010s, when demand had recovered.

即使在需求复苏的 2010 年代末期，美联储仍将利率维持在超低水平。

And it even kept rates low in 2021 as inflation was surging.

2021 年，随着通胀飙升，它甚至将利率保持在较低水平。

There’s an interesting paper to be written there about how sluggishness in the Fed’s reaction function might be a substitute for forward guidance, and act as an automatic stabilizer of sorts.

那里有一篇有趣的论文要写，关于美联储反应功能的迟缓可能如何替代前瞻性指导，并充当某种自动稳定器。

The “multiplier” here is a measure of the effectiveness of stimulus.

这里的“乘数”是刺激措施有效性的衡量标准。

When the multiplier is greater than one, it means a dollar of government spending raises GDP by more than a dollar.

当乘数大于1时，意味着一美元的政府支出使GDP增加一美元以上。