2018年经济学人 代代叠加:投机泡沫(1)（在线收听）

A third, more anarchic way to transfer resources from young to old is a speculative bubble.

第三种、同时也是更为无序地将资源从年轻人转移到老年人的方式是投机泡沫。

In a bubble, people pay over the odds for an asset, such as a house, in the belief that subsequent investors will pay a higher price still.

泡沫中，带着后来的投资者会开出更高的价格的信念，人们为某种资产，如房屋，支付超出其赔率的钱。

The overpayment amounts to a contribution to a Ponzi scheme, redeemed not by the earnings of the underlying asset, but by overpayments from later investors.

这种超额支付相当于对庞氏骗局的出资，它不是由标的资产的收益来偿付的，而是由来自后来的投资者的超额支付来偿付的。

If each generation is collectively richer than the last, then the asset's price can keep rising even if each buyer sinks only the same percentage of their (rising) income into it.

如果每一代人总体上都比上一代人更为富有，那么，就算是每一位买家投入其中的只是其（不断上涨的）的收入的相同百分比，资产的价格也能保持上涨。

All these mechanisms have side-effects.

所有这些机制都有副作用。

Government debt can crowd out productive investment.

政府债务可能挤出生产性投资。

Bubbles can do the same.

泡沫可能作出同样的事情。

But in an economy suffering from dynamic inefficiency, this crowding out is a good thing.

但是，在饱受动态无效率之苦的经济体中，这种挤出是一件好事。

Such an economy has accumulated too much capital.

这样的经济体积累了太多的资本。

It requires heavy investment to keep this large stock of machinery, equipment, buildings and infrastructure growing in line with the economy.

它需要大笔的投资，以保持大量的机器、设备、建筑和基础设施与经济同步增长。

The young are tempted to add yet more capital in an effort to transfer resources to their future, older selves.

诱惑之下，年轻人增加了更多的资本，视图将资源转移给未来的、年老的自己。

Yet because the returns are so low, it is more efficient for them to transfer resources directly to today's elderly (by contributing to social security, buying government bonds or overpaying for the old people's assets), on the understanding that tomorrow's young will do the same for them.

然而，由于回报太低，对他们来说，基于明天的年轻一代会为他们做同样的事的认识，（通过缴纳社会保险，购买政府债券或是对老年人的资产多付钱等方式）把资源直接转移给今天的老年人效率更高。

Under certain conditions, then, Ponzi principles are efficient not maleficent.

因而，在特定条件下，庞氏原理是有效的，而不是有害的。

But are those conditions ever found in the real world?

但是，这些条件曾在现实世界中被发现过吗？

One way to look for them is to compare interest rates (which represent the return on capital) and GDP growth rates (which reflect both population growth and increases in income per person).

寻找它们的一种办法是比较（代表资本回报的利率）和（反映人口与人均收入增长的）GDP增长率。

An alternative, stiffer test (which works well under certain assumptions) is to compare investment and profits.

一种（在一定的假设下运转良好的）具有替代性的和更为严格的验证是比较投资和利润。

If national investment is greater than profits, a country is ploughing more into its stock of capital than it earns from it.

如果国民投资大于利润，国家正在将多于从中挣得钱投入到资本存量之中。

It is as if the islanders are replanting all of the fruit they collect from the additional trees they have cultivated (minus whatever fruit they need to compensate themselves for their labour) plus a few more.

这就好比岛民们正在把比他们能从自己所培育的额外的树上收集到的全部还要多的果实重新种下去一样。

The economy's efforts to save and invest for the future are overloading the available vehicles for thrift.

经济体的为未来储蓄和投资的尝试正负载着过多的可以得到的节俭载体。

Economists used to be confident that most economies were on the right side of this test, earning far more in profit than they invested.

之前，经济学家曾经对大多数经济体在这种验证的正确一边充满自信，认为经济体在利润方面的所得远远超过投入。