对于国家衰落的原因，伏尔泰的观点是：（罗马）帝国之所以崩溃，是因为“一切都崩溃了”。还有一种原因是“没有什么是永恒的”，可这只是无比正确的废话而已。即便如此，如果在思考美国的世界霸权时，能够知道它何时衰落，而美国又能采取哪些方法延缓这一进程，真是再好不过了。
罗马帝国由盛转衰直至最终灭亡用了几百年的时间，美国是不是也能找到这种可以让其全球性的主导地位延绵更久的方法呢？
在探讨这一问题时，学者阿文德•萨勃拉曼尼亚在其新书《日食：生活在中国经济霸权的阴影之下》当中，做出了一个重要的贡献：他制定出一个衡量经济强权的指数体系。对于那些正在思考世界经济领导权变迁的人们来说，这一体系应被视为是其议论的焦点。阅读本书其实并不需要任何经济基础，因为书中的内容都是有关权力的。
有些基本事实毋庸置疑：自19世纪早期工业化兴起后，英国曾一度占据了世界经济的霸主地位，但它最终被美国抢去了头把交椅。至少从1945年以来，美国就一直是全球市场经济国家当中毋庸置疑的领导者。
19世纪末期的时候，美国的工业生产就已超过英国。但这并不足以影响后者的地位。真正让英国的经济霸权易主的原因是“一战”和“二战”，英国在这两次战争中累计了大量的经常性账户赤字——它必须通过大规模的借贷来维持战争的支出，而且进口远大于出口。
最终，当战争结束时，全球大部分的黄金储备都集中到美国人手里。这使得英镑的国际地位大受影响，美元则借机粉墨登场——尤其是1944年建立布雷顿森林体系、各方协定将美元和黄金挂钩之后。
最近情况却发生了逆转：美国越来越依赖于大规模的经常性账户赤字，出口也远远低于进口，它似乎要步英国的后尘了。
与此同时，新兴市场国家的人均收入则在不断地增长之中，它们的国际地位也在得到提升。尤其是在过去的十多年中，由于奉行了保持顺差并且积累外汇储备的战略，中国当前的外储总额已经达到3万亿美元之巨。
而阿文德最具争议性的观点其实是：在经济霸权方面，中国其实已经超过美国。只是我们还未能意识到这一点而已。
许多年前也有人认为日本已经取代美国，而现在的欧洲似乎也掌握了部分的全球经济霸权。但如今看来，这一切都近乎荒缪，因为上述两个地区的信贷系统已经失控：20世纪80年代的日本向私营经济发放了过多的贷款，而在2000年之后，欧元区各国的政府又欠下了巨额的政府债务。
因此，中国的发展能否持续保持平稳尚有待观察。中国固定资产投资额已经接近GDP的50％——这堪称一项世界纪录。与此同时，中国针对国有企业及家庭的放贷也在持续快速增长当中，这不是跟当年日本已经失控的增长类似的情形吗？
在发行一种全球投资者和各国政府都愿意持有的“储备货币”问题上，阿文德认为中国已经具备了许多先决性的条件，这是事实。但中国依然缺乏某些关键性因素，这包括完全意义上的财产所有权。如果你还担心当经济环境变得糟糕时是否会出现无法将资金转移出该国的情形，那么中国就不是恰当的选择。
在某些情况下，来自外部的挑战会拖垮整个国家。但更可能的情形，是该国内部出现巨大变故——政权无法保证经济增长，政府丧失合法性，人民开始设法转移到其他国家（或至少将资金转移出国）。
因此，如果说美国近期要被其他国家所超越，更可能是因为其自身的社会凝聚力丧失及效率低下的政治系统双重原因所导致。中国很可能会填补美国衰落所带来的权力真空，但我们并不能据此认为是它压倒了美国。
西蒙•约翰逊为IMF前首席经济学家、麻省理工学院斯隆商学院教授、彼得森国际经济研究所高级研究员
WASHINGTON, DC – According to Voltaire, the Roman Empire fell “because all things fall.” It is hard to argue with this as a general statement about decline: nothing lasts forever. But it is also not very useful. In thinking, for example, about American predominance in the world today, it would be nice to know when it will decline, and whether the United States can do anything to postpone the inevitable.
Contemporary commenters despaired of the Roman Empire for several hundred years before it finally collapsed. Could America find its way to a similar extension?
In terms of providing an essential structure for discussion of this problem, Arvind Subramanian’s new book, Eclipse: Living in the Shadow of China’s Economic Dominance, is a major contribution. (Full disclosure: Subramanian and I are colleagues at the Peterson Institute for International Economics, and we have worked together on other issues.)
In particular, Subramanian develops an index of economic dominance that should become a focus of conversation anywhere that people want to think about changes in world economic leadership. There is no need to know any economics in order to be fascinated by this book: it is about power, pure and simple.
The basic facts are incontrovertible. The United Kingdom was the world’s dominant economic power from the rise of industrialization in the early nineteenth century. But it lost its predominance and was gradually eclipsed by the US, which, at least since 1945, has been the undisputed leader among market-based economies.
The US surpassed the UK in terms of industrial production as early as the end of the nineteenth century, but that was not enough to tip the balance. Economic predominance shifted only when the UK ran large current-account deficits during World Wars I and II – the country had to borrow heavily in order to finance its war effort, and imports were significantly higher than exports. Much of the world’s gold reserves ended up in the hands of the US.
This helped undermine the role of the British pound internationally and catapulted the US dollar to the fore – particularly after the Bretton Woods conference in 1944, at which it was agreed that countries would hold their reserves in dollars as well as gold.
More recently, however, it has been the Americans’ turn consistently to run large current-account deficits, buying more from the rest of the world than they earn by selling goods and services abroad. On this dimension, the US seems destined to repeat the mistake of the British.
At the same time, emerging-market countries’ per capita income has risen – as has their international role. In particular, China has followed a strategy in the past decade or so that entails running large current-account surpluses and building up foreign-exchange reserves, which are now reported to be in excess of $3 trillion. Indeed, Subramanian’s most provocative argument is that China has already surpassed the US in terms of economic dominance – but we have not yet woken up to this new reality.
The story is fascinating and well told; but there is still a great deal worth arguing. For example, did the British decline because the US could not be stopped, or because of problems within the British Empire and at home?
A few years ago, some regarded Japan as having overtaken the US. Europe also was supposedly vying for global economic dominance. Now any such claims would seem preposterous. In both cases, the credit system got out of control, with too much lending to the private sector in 1980’s Japan and excessive government borrowing during the 2000’s in the eurozone.
Similarly, it remains unclear that the Chinese development path will remain smooth. Fixed investment in China is close to 50% of GDP – which must be a world record. Credit to state firms and to households continues to grow rapidly. Isn’t this a version of exactly what derailed Japanese growth?
On the key issue of being able to issue a “reserve currency” that investors and governments want to hold, Subramanian is correct that China has many of the prerequisites in place. But it still lacks some key elements, including fully-fledged property rights. If you worry about getting your money out of a country when times turn tough, China is not an attractive place to hold your reserves.
External challenges do sometimes bring down states. But, more frequently, the big problems are internal – the regime cannot deliver growth, its legitimacy fades, and people start to head for the exits (or at least get their money out).
If the US is eclipsed any time soon, this will more likely be due to its loss of social cohesion and its dysfunctional politics. China might well step in to fill that vacuum, but that is quite different from being able to elbow America aside.
Simon Johnson, a former chief economist of the IMF, is co-founder of a leading economics blog,http://BaselineScenario.com, a professor at MIT Sloan, a senior fellow at the Peterson Institute for International Economics, and co-author, with James Kwak, of 13 Bankers.
