What is hardest to forecast, though, are turning points – when the old relationships break down. While there may be some factors that signal turning points – a run-up in short-term leverage and asset prices, for example, often presages a bust – they are not infallible predictors of trouble to come.
但即便他们这样做了，他们也会羞于预测。专业经济学家相对于专业市场预测者的主要优势可能在于前者更容易意识到各因素之间已经建立的关联。而预测的最困难之处恰恰是转折点——就是当旧有的关联破裂之时。虽然有些因素会反映转折点的到来——比如说短期金融杠杆和资产价格的上升通常预示着泡沫破裂——但这不意味着危机就一定会爆发。