And there is Tobin's q, a ratio of the stockmarket value to the replacement cost of its tangible assets an attempt to measure what it would cost to recreate a company from scratch.

ECONOMIST: A survey of global equity markets: Valuation waltz | The

These find that, when the ratio (suitably adjusted to take care of accounting discrepancies) moves far above one, equilibrium is indeed eventually restored not, however, by a surge in the replacement value of companies' assets but by a correspondingly dramatic fall in the value that Wall Street places on them.

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