Does Excess Debt Lead to Bubbles?

About a week ago, I was having drinks with a friend and discussing John Kenneth Galbraith's dictum that "all financial innovation involves ... the creation of debt secured in greater or lesser adequacy by real assets," wrote the economist John Kenneth Galbraith in 1993. And "all crises have involved debt that, in one fashion or another, has become dangerously out of scale in relation to the underlying means of payment."

I have espoused this theory at various points, and he agreed with it.  But we came to a sticking point:  what about the stock market bubble?  Debt certainly rose dramatically starting around the same time, but VCs were long money, not superleveraged hedge funds.  Households were obviously tapping quite a bit of credit, but that was unsecured credit or mortgages more than margin loans, so the feedback loop is considerably attenuated.  And the bubbliest companies weren't using debt, because they didn't have any cash flow.

In the Financial Times (registration required), Frederick Mishkin argues that not all bubbles are created equal:

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.

Eventually, the bubble bursts and asset prices collapse, leading to a reversal of the feedback loop. Loans go sour, the deleveraging begins, demand for the assets declines further and prices drop even more. The resulting loan losses and declines in asset prices erode the balance sheets at financial institutions, further diminishing credit and investment across a broad range of assets. The resulting deleveraging depresses business and household spending, which weakens economic activity and increases macroeconomic risk in credit markets. Indeed, this is what the recent crisis has been all about.

The second category of bubble, what I call the "pure irrational exuberance bubble", is far less dangerous because it does not involve the cycle of leveraging against higher asset values. Without a credit boom, the bursting of the bubble does not cause the financial system to seize up and so does much less damage. For example, the bubble in technology stocks in the late 1990s was not fuelled by a feedback loop between bank lending and rising equity values; indeed, the bursting of the tech-stock bubble was not accompanied by a marked deterioration in bank balance sheets. This is one of the key reasons that the bursting of the bubble was followed by a relatively mild recession. Similarly, the bubble that burst in the stock market in 1987 did not put the financial system under great stress and the economy fared well in its aftermath.

Sounds convincing . . . but I can't help wondering why credit and stock market prices were rising at the same time.