ON THE morning of December 7th 1941, George Elliott Junior noticed “the largest blip” he had ever seen on a radar near America’s naval base at Pearl Harbour. His discovery was dismissed by his superiors, who were thus unprepared for the Japanese bombers that arrived shortly after. The mistake prompted urgent research into “receiver operating characteristics”, the ability of radar operators to distinguish between true and false alarms.

1941年12月7日的上午，小乔治·艾略特注意到珍珠港美国海军基地附近的雷达上出现了他所见过的“最大幅度波动”。他的发现没有得到上级的重视，因而美军在紧随其后的日军偷袭面前毫无准备。这个错误推动了紧急研究“信息接收器操作特征”，即雷达操作人员区分真假警报的能力。

A similar concern motivates research at the Bank for International Settlements (BIS) in Basel, Switzerland. Its equivalent to the radar is a set of economic indicators that can potentially detect the approach of financial crises. A prominent example is the “credit gap”, which measures the divergence between the level of credit to households and non-financial firms, expressed as a percentage of GDP, and its long-term trend. A big gap may reflect the kind of unsustainable credit boom that often precedes a crisis. Anything above 9% of GDP is reason to worry, according to Iñaki Aldasoro, Claudio Borio and Mathias Drehmann of the BIS.

类似的担忧推动了位于瑞士巴塞尔的国际清算银行的一项研究。与雷达一样，该项目有一整套经济指数，能检测出潜在的经济危机的。信贷缺口就是一个著名的例子，它衡量了家庭和非金融企业之间信贷水平的差异，用GDP占比和其长期发展趋势表示。巨大的信贷缺口可以反映非可持续性的信贷激增，这往往会加速经济危机的到来。国际清算银行的Iñaki Aldasoro, Claudio Borio 和Mathias Drehmann则表示，任何在GDP中占比超过9%的情况都会引起担忧。

The biggest blips on the oscilloscope include Canada (9.6%), Singapore (11.1%) and Switzerland (16.3%), according to the latest readings, released on March 11th. But the one that has kept everyone’s eyes peeled is China, with a gap of 16.7% in the third quarter of 2017 (the latest BIS figure available).

根据3月11日公布的最新读数，示波器上波动程度最大的经济体包括加拿大（9.6%）、新加坡（11.1%）和瑞士（16.3）。不过，引起所有人关注却是中国。据国际清算银行提供的数据显示，2017年中国第三季度的信贷缺口高达16.7%。

As a crisis-detector, the credit gap has some appealing operating characteristics. It can stand alone. It can be estimated quarterly across many economies. And, according to Mr Aldasoro and his co-authors, it would have predicted 80% of the crises since 1980 in the countries and periods for which data are available.

作为经济危机的一个指标，信贷缺口的某些操作特点引人注目。它可以单独使用，也可以在诸多经济体中按季度考察。根据Aldasoro及其合作者的说法，它将可以预测到1980年以来发生在某些国家和某些时段的80%的经济危机，具体到危机的具体日期。

The problem is that it has also predicted many crises that never arrived. When such early-warning indicators flash red, the chance of a crisis in the next three years is “around 50%”, says Mr Drehmann. The BIS provides over 5,200 credit-gap readings for the period since 1980. In over 850 instances, the gap exceeded 9% but skies remained clear.

问题是，信贷缺口还预测了许多尚未发生的经济危机。Drehmann表示，当这些预警指标的红灯闪烁时，未来三年内危机发生的可能性在50%左右。国际清算银银行自1980年以来的时间段提供了超过5200的信贷缺口读数，在850多个案例中，误差超过了9%，但仍未达到上限。

The problems seem worse in emerging markets. Their data are patchier, covering just 13 crises. Of this unfortunate number, only eight were preceded by a big credit gap. (Another three struck within three years of the start of the data, which may be too early to provide a fair test of the indicator.) There have been many false alarms. The credit gap flashed red almost continuously in Chile in 1993-2002, reaching over 24%, but no crisis followed. It was also persistently large in the Czech Republic in 2007-14 and in Hungary in 2000-10 without any great trauma ensuing. The indicator successfully predicted the “Asian flu” in Indonesia, Malaysia and South Korea in the late 1990s, but only after sounding a false alarm in all three countries in the 1980s.

新兴市场的情况似乎更糟，有关数据残缺不齐，仅仅有13次经济危机。而就在这个不吉利数字中，只有八次经济危机在发生之前就有巨大的信贷缺口（另外三个国家的经济在数据收集工作开始的前三年就被信贷缺口击溃了，其发生时间太早从而无法为指标提供公正的受测结果）。信贷缺口也做过许多错误预警。1993至2002年间，智利的信贷缺口指标几乎一直处于红色预警状态，高过标准的24%，但是危机并没有随之出现。捷克在2007年到2014年和匈牙利2000年到2010年间的指标也持续超标，但有大危机同样没有到来。该指标倒是成功地预测了20世纪90年代后半期发生在印度尼西亚、马来西亚和韩国等亚洲国家的经济危机，但在此之前，信贷缺口也在20世纪80年代发出了一次关于这三个国家经济的错误警报。

What about China? Paul Samuelson, a Nobel-prize winning economist, once joked that the stockmarket had predicted nine out of America’s last five recessions. Similarly, the credit gap predicted at least three out of China’s last zero crises. It rose above 9% in mid-2003, mid-2009 and mid-2012, where it has stayed since. China’s comeuppance may still arrive. But the gap is now closing rapidly. It has decreased from almost 29% in the first quarter of 2016 to less than 13% at the end of last year, according to The Economist’s calculations.

中国的情况怎样呢？诺贝尔经济学奖获得者保罗·塞缪尔森曾开玩笑地表示，股票市场预测了美国有九次衰退 ，可实际上只有五次。类似地，信贷缺口指标预测了中国会有三次经济危机，却一次也没有出现。信贷缺口分别在2003年中期、2009年中期和2012年中期超过9%，并一直保持在这个水平。因此，对于中国来说，该来的还是会来的。不过，中国的信贷缺口在快速缩小。根据《经济学人》的计算，中国的信贷缺口已经从2016年第一季度的几乎高达29%降至2017年年末的不足13%。

One obvious explanation for China’s resilience is that its credit is mostly home-grown, extended by domestic banks and other Chinese lenders. By contrast the crisis-struck emerging economies mostly relied on inflows of foreign capital to finance their current-account deficits with the rest of the world. Looking at both current-account gaps and credit gaps may provide better predictions, says Michael Spencer of Deutsche Bank. He calculates that China’s risk of a financial crisis this year is less than 8% (assuming a credit gap of under 13%) partly because it runs a current-account surplus of about 1.4% of GDP. If China’s government keeps credit stable as a share of GDP this year, this crisis-risk could fall to about 5%.

对于中国经济韧性的一个显而易见的解释是，信贷主要来源于国内增长，是国内银行和其他中国贷款机构推动其扩张。相比之下，受到冲击的其他新兴市场主要依赖外国资本流入，为其经常账户赤字提供资金。德意志银行的迈克尔·斯宾塞表示，同时观测经常项目缺口和信贷缺口，可能会得出更好的预测。他预估，中国今年发生金融危机的风险不超过8%（假定信贷缺口在13%以下），一个原因是中国的经常项目盈余保持在GDP的1.4%左右。如果中国政府今年将信贷缺口保持稳定在GDP的一定比重，危机发生的风险可能降至大约5%。

On that day of infamy in 1941, Mr Elliott took the radar blip far more seriously than his fellow operator did, despite being less experienced. Perhaps this should not be surprising. After less than three months of radar-watching, Mr Elliott was not yet jaded by routine. If a financial crisis eventually strikes China, many people will be caught out—not because of a lack of warnings, but because of too many.

在1941年悲惨的那一天，艾略特尽管经验不足，他在观测雷达信号时比他的同伴们要仔细得多。也许这并不令人感到惊讶。在从事雷达观测不足三个月，艾略特还没有对这样的例行公事产生厌倦。如果金融危机最终袭击了中国的话，许多人都会因此受创，但并不是因为缺少事先警告，而是因为警告太多了。

编译：卢语欣

编辑：翻吧君

来源：经济学人（2018.3.17）