经济学人下载:2021美国的发展牵一发而动全身(2)

The degree to which it is felt, however, depends crucially on the policy response, both at home and abroad. Fiscal spillovers are more powerful when recipient countries are themselves operating below potential. American spending is thus more likely to spill over to the rest of the world if its recovery is much stronger than those of its trading partners. Ordinarily, spillovers provide a strong incentive for governments to co-ordinate their stimulus efforts—lest some tight-fisted economies (eg, those in Europe) free ride on the largesse leaking from more generous ones. Indeed, on February 12th Janet Yellen, America's treasury secretary, urged her counterparts in the G7 group of countries to "go big" on stimulus, too. Countries that free ride could find themselves in hot water with Ms Yellen: the Biden administration has promised to be stern with countries that run large, persistent trade surpluses. 

然而，这种感觉的程度关键取决于国内外的政策反应。当受援国自身的运作低于潜在水平时，财政溢出效应会更为强大。因此，如果美国的复苏比它的贸易伙伴更强劲，那么它的支出更有可能扩散到世界其他地方。通常情况下，溢出效应为政府协调其刺激措施提供了强大的动力——以免一些吝啬的经济体(如欧洲国家)搭上从更为慷慨的经济体中溢出的慷慨便车。事实上，2月12日，美国财政部长珍妮特·耶伦敦促七国集团(G7)的同行们也在刺激政策上“加大力度”。那些搭便车的国家可能会发现自己和耶伦陷入麻烦：拜登政府已承诺，将严厉对待那些长期拥有巨额贸易顺差的国家。

But if America does come close to overheating, then a reluctance to spend elsewhere may be less irksome than usual, as demand-starved countries serve as a release valve for the pressure building up at home. Growth in global trade seems to have enhanced its pressure-relieving capabilities, according to work by Jane Ihrig, Steven Kamin, Deborah Lindner and Jaime Marquez of the FEDeral Reserve. They reckon that the expansion in trade has served to weaken the link between changes in domestic demand and corresponding shifts in total output, with net exports bearing more of the burden of adjustment to changes in domestic spending. In the late 1990s, for instance, measures of domestic demand grew even faster than real GDP (which was itself growing at a rapid clip). Inflation remained relatively subdued, however, in part because America's current account deficit swelled. Similarly, a surge in imports this year might dissipate potential inflationary pressures in America while giving a lift to its weaker trade partners.

但如果美国经济真的接近过热，那么不愿在其他地方消费可能不会像往常那样令人讨厌，因为需求匮乏的国家充当了释放国内积聚的压力的阀门。美联储的简·伊里克、史蒂文·卡明、德博拉·林德纳和杰米·马尔克斯的研究显示，全球贸易的增长似乎增强了中国的减压能力。他们认为，贸易的扩张削弱了国内需求变化和相应的总产出变化之间的联系，使净出口承受了更多的调整国内支出变化的负担。例如，在上世纪90年代末，国内需求指标的增长速度甚至超过了实际GDP(GDP本身也在快速增长)。然而，通货膨胀仍然相对温和，部分原因是美国的经常账户赤字膨胀。同样，今年进口的激增可能会消除美国潜在的通胀压力，同时提振其较弱的贸易伙伴。

The biggest uncertainty about the global effects of a hot American economy is the reaction of the FED. Recent work by Kristin Forbes of the Massachusetts Institute of Technology suggests that domestic inflation has become more responsive over time to global factors—including the amount of economic slack across the global economy as a whole. Yet wage inflation still seems to respond mostly to domestic conditions. The FED might therefore shrug off price rises later this year, reckoning that short-run price pressures will not translate into sustained inflation until America's job market, and the world economy, is fully recovered. A doveish FED should make for a weaker dollar and easier financial conditions worldwide, adding to the boost that comes from Americans buying more goods from abroad. 

美国经济过热对全球影响最大的不确定因素是美联储的反应。麻省理工学院的克莉丝汀·福布斯最近的研究表明，随着时间的推移，国内通货膨胀对全球因素的影响越来越大，包括全球经济整体上的疲软程度。然而，工资上涨似乎仍取决于国内情况。因此，美联储可能会在今年晚些时候对价格上涨不屑一顾，因为在美国就业市场和世界经济完全复苏之前，短期价格压力不会转化为持续的通货膨胀。一个温和的美联储应该会使美元走软，并使全球金融环境更加宽松，从而增加美国人从海外购买更多商品带来的提振。

But a really rip-roaring economy could test the FED's patience, particularly if a yawning current account deficit and soaring asset prices cause it to worry about a build-up of financial risk. The spectre of American interest-rate hikes could frighten global markets, and force emerging economies to adopt less stimulative fiscal and monetary policies. A bit of demand spilling over from America would seem insignificant in comparison. That the FED will suddenly turn hawkish still seems unlikely. But if America's temperature runs high enough, the rest of the world may break out in cold sweats. 

但是，一个真正蓬勃发展的经济可能会考验美联储的耐心，尤其是，不断扩大的经常账户赤字和不断飙升的资产价格会使其担心金融风险的累积。美国加息的幽灵可能会吓坏全球市场，迫使新兴经济体采取较少刺激性的财政和货币政策。相比之下，来自美国的少量需求似乎微不足道。美联储突然转向鹰派的可能性似乎不大，但如果美国的气温升得足够高，世界其他地方可能会冒出一身冷汗。