经济学人下载:代代叠加:"拖"无止境(2)

America's Social Security, for example, is largely pay-as-you-go.
例如，美国的社会保险制度（Social Security）就是一个大型的现收现付制度。

For this reason, its critics often compare it to a Ponzi scheme in order to discredit it.
因为这个原因，它的批评者经常将其比作庞氏骗局，以便败坏它的名声。

But the comparison can also work the other way.
但是，这种比较也可以用另一种方式来进行。

If Social Security—a venerable entitlement that has spared millions from penury—bears some resemblance to a Ponzi scheme, then perhaps Ponzi principles are not always as diabolical as the name suggests.
如果说社会保险制度——这项让数百万人远离了贫困的久负盛名的福利制度——类似于庞氏骗局，那么，庞氏原理可能并非总是如其名字所示的那样臭名昭著。

In some cases, those principles might indeed redound to everyone's benefit.
在某些情况下，这些原理或许的确有助于每一个人的福利。

One such scenario was sketched by Paul Samuelson of the Massachusetts Institute of Technology in 1958.
这样的一幕曾在1958年被麻省理工的保罗·萨缪尔森勾勒出来过。

His thought experiment is easiest to understand when recast as an island parable (along lines suggested by Laurence Kotlikoff of Boston University) .
他的思想实验在改写为一个岛国寓言（再加上波士顿大学的劳伦斯-克特里考夫所做的旁白）时是最容易理解的。

The island in this parable is home to unusually tall cacao trees, hungry people, and little else.
寓言中的这座岛是参天的恒星树和饥饿之人的家园。除此之外，再没有其他。

Only the young can climb the trees and pick the fruit, which must be eaten quickly before it spoils in the hot sun.
在岛上，只有年轻人能爬到树上摘取果实，而果实又必须要在炎热的太阳下腐烂之前就被吃掉。

And only two generations (young and old) are alive at the same time.
同时，只有两代人（年轻的和年老的）在同一时间是活着的。

On such an island, the elderly have no way to provide for themselves.
在这样一座岛上，老年人无法养活自己。

They are physically incapable of picking fruit.
从身体上来说，他们无力摘取果实。

They cannot buy fruit from the young, because they have nothing to offer in exchange.
由于没有什么东西可供交换，他们不可能从年轻人那里买到果实。

Nor can they live off any cacao pods saved from their youth, because their stockpile will have rotted by the time they are old.
同时，由于他们的存货到他们老了的时候已经腐烂，他们也无法靠着从年轻时就储存起来的恒星豆荚生活。

There are no durable, imperishable assets that might serve as a vehicle for their thrift.
那里没有任何可能充当他们的节俭的载体的持久的、不腐烂的资产。

The solution, of course, is an intergenerational Ponzi scheme.
答案必然是一种代际庞氏骗局。

The young give fruit to the old on the understanding that the next generation will do the same for them when they grow frail.
基于下一代会在自己年老体衰时对他们做同样的事情的认识，年轻人把果实交给老年人。

In effect, the young lend to their parents and collect repayment from their children.
实际上，年轻人是把钱借给他们父母并从自己的孩子那里筹集偿付。

In so doing, they serve as a link between two generations that never otherwise coexist.
在做这种事的时候，他们所充当的就是从未共同存在的两代人之间的联系的角色。

The scheme works, Samuelson pointed out, only because “new generations are always coming along”.
萨缪尔森指出，骗局仅仅是因为“新一代总是在前行”才有效。

If reproduction were ever to cease, the last generation would get nothing out of the scheme.
如果人类繁衍停止，最后一代人从骗局中会一无所获。

Knowing this, they would not put anything in.
了解了这一点，他们就不会投入任何东西。

But their failure to contribute would also deprive the penultimate generation of a payout, leaving them no reason to take part either.
但是，他们停止出资也会剥夺倒数第二代人的偿付，令他们也没有理由参与其中。

Any anticipated future break in the chain causes the whole thing to uncouple.
任何预料之中的未来的链条断裂让整件事情无以为续。

If the scheme must ever end, it cannot even start.
如果骗局必须终结，它就不可能开始。