The widespread failure of economists to forecast the financial crisis that erupted last year has much to do with faulty models. This lack of sound models meant that economic policymakers and central bankers received no warning of what was to come.
As George Akerlof and I argue in our recent book Animal Spirits, the current financial crisis was driven by speculative bubbles in the housing market, the stock market, energy and other commodities markets. Bubbles are caused by feedback loops: rising speculative prices encourage optimism, which encourages more buying and hence further speculative price increases — until the crash comes.
You won’t find the word “bubble,” however, in most economics treatises or textbooks. Likewise, a search of working papers produced by central banks and economics departments in recent years yields few instances of “bubbles” even being mentioned. Indeed, the idea that bubbles exist has become so disreputable in much of the economics and finance profession that bringing them up in an economics seminar is like bringing up astrology to a group of astronomers.
The fundamental problem is that a generation of mainstream macroeconomic theorists has come to accept a theory that has an error at its very core — the axiom that people are fully rational. As the statistician Leonard “Jimmie” Savage showed in 1954, if people follow certain axioms of rationality, they must behave as if they knew all the probabilities and did all the appropriate calculations.
So economists assume that people do indeed use all publicly available information and know, or behave as if they know, the probabilities of all conceivable future events. They are not influenced by anything but the facts, and probabilities are taken as facts. They update these probabilities as soon as new information becomes available and so any change in their behavior must be attributable to their rational response to genuinely new information. If economic actors are always rational, then no bubbles — irrational market responses — are allowed.
Abundant psychological evidence, however, has now shown that people do not satisfy Savage’s axioms of rationality.
In fact, people almost never know the probabilities of future economic events. They live in a world where economic decisions are fundamentally ambiguous, because the future doesn’t seem to be a mere repetition of a quantifiable past. For many people, it seems that “this time is different.”
The work of Duke neuroscientists Scott Huettel and Michael Platt has shown, through functional magnetic resonance imaging experiments, that “decision making under ambiguity does not represent a special, more complex case of risky decision making; instead, these two forms of uncertainty are supported by distinct mechanisms.”
In other words, different parts of the brain and emotional pathways are involved when ambiguity is present.
Mathematical economist Donald Brown and psychologist Laurie Santos, both of Yale, are running experiments with human subjects to try to understand how human tolerance for ambiguity in economic decision making varies over time.
They theorize that “bull markets are characterized by ambiguity-seeking behavior and bear markets by ambiguity-avoiding behavior.”
These behaviors are aspects of changing confidence, which we are only just beginning to understand.
To be sure, the purely rational theory remains useful for many things. It can be applied with care in areas where the consequences of violating Savage’s axiom are not too severe. Economists have also been right to apply his theory to a range of microeconomic issues, such as why monopolists set higher prices.
The theory, however, has been overextended. For example, the “Dynamic Stochastic General Equilibrium Model of the Euro Area,” developed by Frank Smets of the European Central Bank and Raf Wouters of the National Bank of Belgium, is very good at giving a precise list of external shocks that are presumed to drive the economy, but nowhere are bubbles modeled. The economy is assumed to do nothing more than respond in a completely rational way to these external shocks.
Milton Friedman and Anna Schwartz, in their 1963 book A Monetary History of the United States, showed that monetary-policy anomalies — a prime example of an external shock — were a significant factor in the Great Depression of the 1930s. Economists such as Barry Eichengreen, Jeffrey Sachs and Ben Bernanke have helped us to understand that these anomalies were the result of individual central banks’ efforts to stay on the gold standard, causing them to keep interest rates relatively high despite economic weakness.
To some, this revelation represented a culminating event for economic theory. The worst economic crisis of the 20th century was explained — and a way to correct it suggested — with a theory that does not rely on bubbles.
Yet events like the Great Depression, as well as the recent crisis, will never be fully understood without understanding bubbles. The fact that monetary policy mistakes were an important cause of the Great Depression does not mean that we completely understand that crisis, or that other crises fit that mold.
In fact, the failure of economists’ models to forecast the current crisis will mark the beginning of their overhaul. This will happen as economists’ redirect their research efforts by listening to scientists with different expertise. Only then will monetary authorities gain a better understanding of when and how bubbles can derail an economy and what can be done to prevent that outcome.
Robert Shiller is professor of economics at Yale University and chief economist at MacroMarkets.COPYRIGHT: PROJECT SYNDICATE
Since COVID-19 broke out in Taiwan, there has been a fair amount of news regarding discrimination and “witch hunts” against medical personnel, people under self-quarantine and other targets, such as the students of a school where an infection was discovered. Quarantine breakers are almost certainly on the loose and it is only natural for people to be vigilant. One in Chiayi was found by accident at a traffic stop because his helmet was not fastened. However, those who follow the rules by quarantining themselves should be encouraged to keep up the good work in a difficult situation, instead of being
Chinese Nationalist Party (KMT) Legislator-at-large Wu Sz-huai (吳斯懷) has said that there is a huge difference between Chinese military aircraft circling Taiwan along the edges of its airspace and invading Taiwan’s airspace. He also said that whether it is US or Chinese aircraft flying along or encircling Taiwan’s airspace, there is no legal basis to say that such actions imply a clear provocation of Taiwan, and asked the Ministry of National Defense not to mislead the public. People who hear this might think that it is not a very Taiwanese thing to say. US military activity in the vicinity of Taiwan
As the nation welcomes home Taiwanese who had been stranded in China’s Hubei Province — arguably one of the most dangerous places on Earth since the novel coronavirus outbreak began in its capital, Wuhan, late last year — problems surrounding the “quasi-charter flights” that brought them back have been largely overlooked. The media used the term to describe the two flights dispatched by Taiwan’s state-run China Airlines because they do not count as charter flights. Taiwanese wanting to board those flights had to travel — most likely by train — more than 1,000km from Hubei to Shanghai Pudong International Airport
As the COVID-19 pandemic spins out of control, many parts of the world are experiencing shortages of medical masks and other protective equipment. I am studying in Washington state, which at the time of writing is the US state that has suffered the largest number of deaths from the novel coronavirus. The week before last, UW Medicine — an organization that includes the University of Washington School of Medicine and associated medical centers and clinics — sent its volunteers an e-mail asking the public to make masks and donate them to hospitals. Attached to the message was a mask donation
RSS