【经济学人】未来经济的预测丨2017.5.18丨总第913期

In his new book, “The End of Theory”, Richard Bookstaber approaches the issue from a different direction, as someone who has managed risk at leading investment banks and hedge funds. He believes that “traditional economic theory, bound by its own methods and structure, is not up to the task” of predicting crises.
布克斯塔伯在他的新书《理论的终结》中，从不同的角度来处理这个问题，就像曾经在顶级投资银行和对冲基金管理过风险的人的看法一样。他认为“传统经济理论受其自身的方法和结构约束，不能预测危机”。

The author argues that the economy is subject to four important phenomena that make traditional economic models useless. The first are “emergent phenomena”. The sum of human interactions can produce unexpected results that are not related to the intentions of the indivuals involved, just as traffic on a motorway can bunch, or crowds can suddenly stampede. The second phenomenon is “non- ergodicity ”. An ergodic process follows the same rule every time. If you roll traditional dice, the odds of getting a three will always be one in six. But in the world of human interactions, probabilities constantly change. A linked phenomenon is known as “radical uncertainty”; people do not know the range, or the probability, of future outcomes. The fourth is “computational irreducibility ”; the future is so complex, and the effect of human interactions so unfathomable , that people cannot possibly create models to anticipate the outcome.
作者认为，经济受制于四个重要现象，它们会使得传统经济模式无效。第一个是“突生现象”。人们的交际可以产生预想不到的结果，这与介入其中的个体的目的没有关系，就像高速公路上的交通可能会堵车，人群可能会突然逃窜。第二种现象是“非遍历性”。遍历过程每次都遵循相同的规则。如果你滚动传统的骰子，获得数字三的机会总是六分之一。但在人类互动世界中，概率不断变化。一种连锁现象被称为“根本不确定性”;人们不了解将来结果的范围或概率。第四是“计算不可化归性”;未来如此复杂，人际交往的效果如此复杂难懂，人们不可能创造模型来预测结果。

• Ergodicity 遍历性;各态历经

• Irreducibility 不可还原性;非还原性

• Unfathomable 深得无法到达底部的;高深莫测的，难以了解的;

Mr Bookstaber is also keen on the concept developed by George Soros, a hedge- fund manager, of “reflexivity”—the idea that observations and beliefs about the state of the economy change behaviour, and those changes in behaviour affect the economy. For example, a belief that house prices will always go up makes buyers willing to pay high prices for homes, and banks more willing to lend; the resulting enthusiasm among debtors and creditors duly pushes house prices higher.
布克斯塔伯先生也支持由对冲基金管理者乔治·索罗斯提出的“反身性”概念，即对国家经济状况的观察和信念会改变行为以及这些行为变化又会影响经济的观点。例如，相信房价一直上涨，买家愿意为房屋支付高价，银行更愿意借贷;债务人和债权人之间的积极性正好推高了房价。