There is increasing concern that we may be experiencing another round of asset-price bubbles that could pose great danger to the economy. Does this danger provide a case for the US Federal Reserve to exit from its zero-interest-rate policy sooner rather than later, as many commentators have suggested? The answer is no.

Are potential asset-price bubbles always dangerous? Asset-price bubbles can be separated into two categories. The first and dangerous category is one I call “a credit boom bubble”, in which exuberant expectations about economic prospects or structural changes in financial markets lead to a credit boom. The resulting increased demand for some assets raises their price and, in turn, encourages further lending against these assets, increasing demand, and hence their prices, even more, creating a positive feedback loop. This feedback loop involves increasing leverage, further easing of credit standards, then even higher leverage, and the cycle continues.