The internet economic debate du jour is summed up nicely by economist Paul Krugman as follows here:
why [doesn't] a housing boom -- which requires shifting resources into housing -- ... produce the same kind of unemployment as a housing bust that shifts resources out of housing.
why ... isn't [ there ] mass unemployment when bubbles are growing as well as shrinking -- why didn't we need high unemployment elsewhere to get those people into the nail-pounding-in-Nevada business?
His point is, on balance, both booms and busts involve the reallocation of resources, yet only busts seem to produce mass unemployment. While Krugman and Arnold Kling* are wrapped up in a debate about how the question influences our understanding of government stimulus, I'd like to simply offer up an answer.
For any fixed amount of capital available for investment, an increase in the amount of capital allocated to one area implies that the amount of capital allocated to some other area must have decreased. In short, capital allocation with a fixed amount of capital is a zero sum game. The same is true of society's capital. If the pie doesn't grow, but stays fixed, and society shifts more of its capital into one area of economic activity, it necessarily implies that we have taken capital away from some other activity.
Asset bubbles, however, are, according to my theory of the world, able to temporarily increase the amount of capital society has available for investment because of the effect that asset bubbles have on the market's expectation of incurring losses on investments tied to the bubble-asset. Some of the capital that society has available for investment is held back by the market in cash or cash-like investments, such as short term Treasuries, in order to cover potential losses that might arise from investments. Some entities, such as banks and insurers, are subject to regulations that dictate how much capital must be set aside to cover these potential losses. Other entities are free to estimate the amount of capital that needs to be held back in order to cover these losses. So, if we took a snap shot of all of society's capital available for investment at a given point in time, some portion of that would be withheld as a loss reserve in cash or cash like investments. That means some portion of the capital available for investment isn't really being allocated to "investments," but being withheld to cover potential losses on bona fide investments.
Asset bubbles create value out of thin air. Price trends develop that deviate sharply from historical norms, and eventually a new, albeit temporary, norm is established. As a result, asset bubbles make the bubble-asset look like a much better investment than it will eventually turn out to be in the long term. As such, asset bubbles create capital available for investment out of thin air because they cause the market to underestimate the amount of capital that has to be set aside to cover potential losses arising from investments tied to the bubble-asset. This means that the effective pie, the portion that actually gets invested in non-cash assets, can be temporarily expanded, removing the zero sum accounting restriction, simply because less of society's resources are used to cover losses.