The China shock has not been debunked. But it is worth understanding the caveats

中国贸易冲击论还没有露出真相，不过还是有必要了解这些警告。

COMPETITION from Chinese imports may have cost some Americans jobs, but economists have done pretty well out of it. Since 2013 David Autor, David Dorn and Gordon Hanson have published nine separate studies digging into the costs of trade. They have found that, of the fall in manufacturing jobs between 1990 and 2007, one-quarter could be attributed to a surge in imports from China. Other sectors failed to soak up the extra workers. Their research also suggested that the China shock has cut the supply of marriageable men and opened the door of the White House to Donald Trump.

中国进口造成的竞争可能导致很多美国人失去工作，但是，经济学家从中挖掘出不少东西。自2013年以来，大卫·奥特尔（David Autor）、大卫·多恩（David Dorn）和戈登·汉森（Gordon Hanson）分别发表了九篇研究深入探究贸易的代价。他们发现，1990-2007年间，四分之一制造业工作岗位的减少可以归因于中国进口的激增。其他领域也无法消化这些失业的员工。三位学者的研究也表明，正是中国的贸易冲击导致适婚男子数量减少，促使唐纳德·特朗普入主白宫。

In recent weeks a dispute has erupted over their results. Jonathan Rothwell, an economist at Gallup, a pollster, alleged “serious flaws” in one paper, prompting a fierce eight-page response from the authors, and an acrimonious public tiff.

最近几周，他们的研究结论引发了争论。民意调查机构盖洛普民的经济学者乔纳森·罗思韦尔（Jonathan Rothwell）声称，其中一份论文中存在“严重的缺陷”，这引来三位作者长达八页的言辞激烈的文章回复，展开了一场激烈的公开争执。

The row centres on how the effect of the China shock is measured. The trio wanted to isolate the effects of extra Chinese supply, rather than of something happening in America, so they checked that imports of particular Chinese products were surging in other rich countries, too. They then compared places in America more exposed to these Chinese imports—typically those with lots of labour-intensive manufacturing—with less exposed ones.

争论的焦点在于对中国贸易冲击效应的衡量。三位作者想要单独计算出额外的中国进口产品的影响，而不是在美国发生的情况。因此，在发现某些中国产品对其他富裕国家的出口也出现激增情况。之后，他们又比较了美国不同地区：从更易受到中国进口影响的地区——特别是劳动密集型地区——到不易受到中国进口影响的地区。

Mr Rothwell’s critique does not attempt to debunk their research completely. But he asks whether combining changes in the 1990s and the 2000s makes sense. When he splits this period up, he confirms the finding that Chinese imports had large effects on American manufacturing employment. But several other effects of Chinese imports become smaller or no longer statistically significant. For example, the effect of Chinese imports on the size of the labour force falls to a quarter of its 1990s size in the 2000s. This is hardly conclusive—slashing sample sizes inevitably reduces the power of a test.

罗思韦尔的评论并不是想要彻底否定他们的研究，而是在质疑将20世纪90年代和21世纪00年代的变化相加是否有意义。将这段时期分隔开后，他确实发现中国的出口对于美国制造业的就业有很大的影响。但是，中国出口的其他一些影响正在逐渐变小，甚至无关紧要。例如，在21世纪00年代，中国出口对于劳动力规模的影响降到了20世纪90年代规模的四分之一。这几乎不能令人信服——削减样本规模无疑会降低试验效果。

Mr Rothwell has not disproved anything. But he has provided an opportunity to think through the assumptions of the original research by Messrs Autor, Dorn and Hanson. Their attempt to isolate the effects of China would not have been entirely successful, for instance, if other countries were experiencing non-China-related shocks similar to those hitting America.

罗思韦尔还没有驳倒任何观点，但是他提供了一种机会，让人们重新思考奥特尔、多恩和汉森的研究中的假设。例如，如果其他国家也在经历与中国无关的贸易冲击，却有与美国类似的遭遇，那么，他们就无法做到单独估算中国的影响。

More broadly, it is impossible to know what would have happened had Chinese imports not surged. Monetary policy might have been different. And what a company such as Apple would have done without low-cost Chinese assembly workers is unknowable. Moreover, adding up individual effects over the whole economy could miss important interactions.

进一步来说，如果中国的出口没有激增，那么会发生什么也无从得知。也许美国会有完全不同的货币政策。此外，如果没有中国廉价的流水线工人，那么像苹果这一类企业会发展到哪一步也无从得知。另外，将个人受到影响与整个经济相加计算，则会忽略一些重要的相互影响。

Mr Rothwell’s strongest criticism is not of that China-shock literature at all, so much as of the way it was received. Some have taken evidence of disruption as proof that tariffs would be a good idea, or that trade with China has hurt America. But, as Mr Autor says himself, “our research does not tell you the net societal costs and benefits of trade.” It does not estimate the benefits to exporters as China opened up (though this was smaller than the rise in imports) or to American shoppers able to buy cheaper stuff.

罗思韦尔最强烈的批评根本不是针对关于中国贸易冲击的论文，而是针对人们对此的反应。有人将这个作为突破性的证据，用以证明提高关税的想法不错，或是对华贸易会损害美国利益。但是，正如奥特尔亲自所言，“我们的研究并不包含贸易带来的社会成本和收益。”研究没有计算中国的开放对美国的出口商（尽管出口低于进口的上涨）或者美国的消费者能够买到更便宜的商品等等好处。

Other research is emerging that attempts to answer those questions. One paper, by Kyle Handley and Nuno Limão, found that the extra trading certainty associated with China’s accession to the WTO lowered American manufacturing sales and employment by more than 1%, but also lowered American prices and raised consumers’ incomes by the equivalent of a 13-percentage-point cut in tariffs. It also helped poor Chinese workers get richer, which isn’t to be sniffed at either.

其他试图回答这些问题的研究也不断出现。凯尔·汉德利（Kyle Handley）和布·里茂（Nuno Limão）共同发表了一篇论文。他们认为中国加入WTO确实产生了额外贸易，而这导致美国制造业的销售和就业至少下降了1%。但是。与此同时，也降低了美国产品的价格，提高了美国消费者的收入，相当于关税削减13%的效果。这也帮助中国工人变得富裕，而没有人会对此抱怨。

编译：王雅文

编辑：翻吧君

来源：经济学人