低增長(zhǎng)是后危機(jī)時(shí)代的現(xiàn)實(shí)

Once the acute phases of the financial and eurocrises were over, it was clear that it would take timefor advanced economies to recover. The history ofpast financial crises gave a clear warning thatrecovery would typically be long and painful.

在金融危機(jī)和歐元危機(jī)過(guò)了嚴(yán)重的階段后，發(fā)達(dá)經(jīng)濟(jì)體顯然需要時(shí)間來(lái)實(shí)現(xiàn)復(fù)蘇。以往金融危機(jī)的歷史提供了明確的警示：復(fù)蘇進(jìn)程通常漫長(zhǎng)而痛苦。

Today, the scars are largely healed but growth is stillslow. Before the crisis, any economist would havepredicted that an economy with interest rates close to zero and no other major brakes ondemand would see high growth rates and quickly overheat. Yet this is not what we have seen.The reason, I believe, must be found in mediocre medium term prospects, which in turnaffect current demand and growth.

如今，危機(jī)造成的創(chuàng)傷已基本痊愈，但經(jīng)濟(jì)增長(zhǎng)依然緩慢。在危機(jī)爆發(fā)前，任何一位經(jīng)濟(jì)學(xué)家都會(huì)這樣預(yù)測(cè)：在利率接近零又不存在其他重大需求抑制因素的背景下，經(jīng)濟(jì)無(wú)疑將快速增長(zhǎng)，并且很快就會(huì)過(guò)熱。然而我們看到的卻不是這樣。我認(rèn)為原因一定出在不太好的中期前景，后者反過(guò)來(lái)影響了當(dāng)前的需求和增長(zhǎng)。

Estimates of long term potential growth in advanced countries have come down by 0.5 to 1per cent since 2007. Some of the decline is due to ageing, some to lower productivity growth.The effect of an ageing population was largely predictable, and indeed largely predicted. (Whether it was taken into account by firms thinking about their investment plans is unclear.)

自2007年以來(lái)，對(duì)發(fā)達(dá)國(guó)家長(zhǎng)期潛在經(jīng)濟(jì)增長(zhǎng)率的預(yù)估下調(diào)了0.5-1%。一部分原因是人口老齡化，還有一部分原因是生產(chǎn)率增速下降。人口老齡化的影響大體上是可預(yù)見(jiàn)的，而且基本上也被預(yù)測(cè)到了。(不清楚企業(yè)在制定投資計(jì)劃時(shí)是否會(huì)考慮人口老齡化因素。)

Productivity growth has been much lower since 2007, more so in Europe where the rate hasdeclined by over 1 per cent in major countries, than in the US, where it has only declined by0.5 per cent. This decline reflects in part cyclical factors and the effect of lower capitalaccumulation. But there is more to it: for the US at least, the evidence points to a slowdownin underlying productivity, starting before the crisis and reflecting the end of a period ofsuccessful implementations of IT innovations. The safe assumption is that the high pre-crisisproductivity growth rate was unusual, and we should expect lower underlying productivitygrowth in future.

生產(chǎn)率增速自2007年以來(lái)下降了很多，而且在歐洲下降得比在美國(guó)厲害——歐洲主要國(guó)家的生產(chǎn)率增速下滑超過(guò)了1%，而美國(guó)只下降了0.5%。生產(chǎn)率增速下降在一定程度上反映了周期性因素以及資本積累減少的影響。但還有更多原因：至少就美國(guó)而言，證據(jù)表明潛在生產(chǎn)率出現(xiàn)了放緩，從金融危機(jī)爆發(fā)前就開(kāi)始了，反映了一段IT創(chuàng)新得到成功應(yīng)用的時(shí)期的結(jié)束?？梢詳喽?，金融危機(jī)前處于高水平的生產(chǎn)率增速并不尋常，我們應(yīng)該預(yù)計(jì)未來(lái)潛在生產(chǎn)率增速會(huì)降低。

Low potential growth is bad news for the medium term. But it may explain what is happeningtoday. A main finding of a paper that Eugenio Cerutti, Lawrence Summers and I wrote in 2015was that, over the past 40 years, recessions in advanced countries have been associatedsurprisingly often with lower growth following the recession.

潛在經(jīng)濟(jì)增長(zhǎng)率較低對(duì)中期來(lái)說(shuō)是壞消息。但它或許可以解釋當(dāng)前的情形。我與歐金尼奧•切魯?shù)?EugenioCerutti)、勞倫斯•薩默斯(Lawrence Summers)2015年合寫(xiě)的一篇論文的一個(gè)主要結(jié)論是，在過(guò)去40年中，發(fā)達(dá)國(guó)家的經(jīng)濟(jì)衰退出奇頻繁地與衰退結(jié)束后增速較低有關(guān)。

One interpretation is the presence of hysteresis, namely that the recession affects potentialgrowth. Another is that the causality runs in reverse: bad news about future potentialgrowth leads to a recession. So, for example, when companies realise that sales prospects areworse than they thought, they cut down on investment. And consumers, realising that theirincome prospects have worsened, cut on consumption.

一種解釋是存在滯后現(xiàn)象，即經(jīng)濟(jì)衰退影響潛在增速。另一種解釋是二者的因果關(guān)系正好倒過(guò)來(lái)：關(guān)于未來(lái)潛在增速的壞消息導(dǎo)致了經(jīng)濟(jì)衰退。比如說(shuō)，當(dāng)企業(yè)意識(shí)到銷售前景比他們認(rèn)為的更糟糕時(shí)，他們會(huì)減少投資。而意識(shí)到自己收入前景惡化的消費(fèi)者會(huì)減少消費(fèi)。

Monetary policy can limit the drop, but not eliminate it. In a 2013 paper I co-wrote, weshowed formally that this interpretation fits postwar US data well. I believe that it alsoexplains what we observe today. The result in this case is not a recession, but a weakrecovery.

貨幣政策可以限制這種下滑，但無(wú)法消除。在我2013年與人合寫(xiě)的一篇論文中，我們嚴(yán)謹(jǐn)?shù)靥岢?，這種解釋與美國(guó)戰(zhàn)后的數(shù)據(jù)相當(dāng)契合。我相信它也可以解釋我們今日所看到的情況。只不過(guò)在這里結(jié)果并非衰退，而是疲弱復(fù)蘇。

This weak recovery in advanced countries also goes a long way in explaining the slowdown inemerging markets. While domestic factors play a role, and the evolution of China is largelysui generis, lower exports, less demand for commodities, and a resulting drop in commodityprices, have led to lower output.

發(fā)達(dá)國(guó)家的疲弱復(fù)蘇對(duì)于解釋新興市場(chǎng)增長(zhǎng)放緩也大有幫助。雖然有國(guó)內(nèi)因素的作用，而且中國(guó)的情況很大程度上具有獨(dú)特性，但出口下滑、大宗商品需求減少以及由此帶來(lái)的大宗商品價(jià)格下跌，已經(jīng)導(dǎo)致產(chǎn)出下滑。

If this new narrative is right, the baseline forecast is for a slow but continued recovery, asthe adjustment to the reality of lower potential growth plays out in advanced economies,and the adjustment to the commodity bust works itself out in emerging market anddeveloping economies. It suggests that some of the scary talk, and some of the exotic policymeasures being discussed, from helicopter money to large negative nominal rates, are not theorder of the day. They should be kept in reserve in case bad things happen, but theexpectation should be that they will not be needed.

如果這種新的分析正確的話，基準(zhǔn)預(yù)測(cè)就是經(jīng)濟(jì)將會(huì)緩慢而持續(xù)地復(fù)蘇，發(fā)達(dá)經(jīng)濟(jì)體將逐漸適應(yīng)潛在增長(zhǎng)率下降的現(xiàn)實(shí)，新興市場(chǎng)和發(fā)展中國(guó)家將逐漸適應(yīng)大宗商品泡沫破裂。這表明，一些引發(fā)恐慌的言論及部分正在討論的非常規(guī)政策措施——從“直升機(jī)撒錢”到較大負(fù)值的名義利率——并不是當(dāng)下最重要的事。這些政策應(yīng)該留待形勢(shì)嚴(yán)峻的時(shí)候使用，但我們最好期待不需要使用到這些措施。

The focus should be increasingly on medium term growth, and the redefinition of normal fiscaland monetary policies in an environment of lower growth and lower interest rates.

我們應(yīng)該更多地著眼于中期增長(zhǎng)，以及在低增長(zhǎng)、低利率的環(huán)境下如何重新定義正常的財(cái)政和貨幣政策。