From this post at Econlog, I was directed to Hyman Minksy:
Minsky argued that a key mechanism that pushes an economy towards a crisis is the accumulation of debt. He identified three types of borrowers that contribute to the accumulation of insolvent debt: hedge borrowers; speculative borrowers; and Ponzi borrowers.
The "hedge borrower" can make debt payments (covering interest and principal) from current cash flows from investments. For the "speculative borrower", the cash flow from investments can service the debt, i.e., cover the interest due, but the borrower must regularly roll over, or re-borrow, the principal. The "Ponzi borrower" (named for Charles Ponzi, see also Ponzi scheme) borrows based on the belief that the appreciation of the value of the asset will be sufficient to refinance the debt but could not make sufficient payments on interest or principal with the cash flow from investments; only the appreciating asset value can keep the Ponzi borrower afloat. Because of the unlikelihood of most investments' capital gains being enough to pay interest and principal, much of this type of finance is fraudulent.
If the use of Ponzi finance is general enough in the financial system, then the inevitable disillusionment of the Ponzi borrower can cause the system to seize up: when the bubble pops, i.e., when the asset prices stop increasing, the speculative borrower can no longer refinance (roll over) the principal even if able to cover interest payments. As with a line of dominoes, collapse of the speculative borrowers can then bring down even hedge borrowers, who are unable to find loans despite the apparent soundness of the underlying investments.
That line of thinking sounds so self-evidently true to me.
And then this:
Economist Paul McCulley described how Minsky's hypothesis translates to the subprime mortgage crisis.[10] McCulley illustrated the three types of borrowing categories using an analogy from the mortgage market: a hedge borrower would have a traditional mortgage loan and is paying back both the principal and interest; the speculative borrower would have an interest-only loan, meaning they are paying back only the interest and must refinance later to pay back the principal; and the ponzi borrower would have a negative amortization loan, meaning the payments do not cover the interest amount and the principal is actually increasing. Lenders only provided funds to ponzi borrowers due to a belief that housing values would continue to increase.
... McCulley also points out that human nature is inherently pro-cyclical, meaning, in Minsky's words, that "from time to time, capitalist economies exhibit inflations and debt deflations which seem to have the potential to spin out of control. In such processes, the economic system's reactions to a movement of the economy amplify the movement – inflation feeds upon inflation and debt-deflation feeds upon debt deflation." In other words, people are momentum investors by nature, not value investors. People naturally take actions that expand the apex and nadir of cycles
The phrases I highlighted feel very important. I think the person who develops a way to detect "momentum gains" from "value gains" in an asset price movement will find himself very, very rich...
