Low interest rates created an incentive for banks, hedge funds and other investors to hunt for riskier assets that offered higher returns. They also made it profitable for such outfits to borrow and use the extra cash to amplify their investments, on the assumption that the returns would exceed the cost of borrowing. The low volatility of the Great Moderation increased the temptation to “leverage” in this way. If short-term interest rates are low but unstable, investors will hesitate before leveraging their bets. But if rates appear stable, investors will take the risk of borrowing in the money markets to buy longer-dated, higher-yielding securities. That is indeed what happened.