LONDON – Early last month, Andy Haldane, Chief Economist at the Bank of England, blamed “irrational behavior” for the failure of the BoE’s recent forecasting models. The failure to spot this irrationality had led policymakers to forecast that the British economy would slow in the wake of last June’s Brexit referendum. Instead, British consumers have been on a heedless spending spree since the vote to leave the European Union; and, no less illogically, construction, manufacturing, and services have recovered.
Haldane offers no explanation for this burst of irrational behavior. Nor can he: to him, irrationality simply means behavior that is inconsistent with the forecasts derived from the BoE’s model.
It’s not just Haldane or the BoE. What mainstream economists mean by rational behavior is not what you or I mean. In ordinary language, rational behavior is that which is reasonable under the circumstances. But in the rarefied world of neoclassical forecasting models, it means that people, equipped with detailed knowledge of themselves, their surroundings, and the future they face, act optimally to achieve their goals. That is, to act rationally is to act in a manner consistent with economists’ models of rational behavior. Faced with contrary behavior, the economist reacts like the tailor who blames the customer for not fitting their newly tailored suit.
Yet the curious fact is that forecasts based on wildly unrealistic premises and assumptions may be perfectly serviceable in many situations. The reason is that most people are creatures of habit. Because their preferences and circumstances don’t in fact shift from day to day, and because they do try to get the best bargain when they shop around, their behavior will exhibit a high degree of regularity. This makes it predictable. You don’t need much economics to know that if the price of your preferred brand of toothpaste goes up, you are more likely to switch to a cheaper brand.