Yet the market for those works may fall abruptly, owing to a lack of originality and creativity after a run-up in prices.

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When prices rise too quickly, or fall too rapidly, the game abruptly ends on a stern warning about social stability.

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What the euro's disciples underestimated, however, is how abruptly and severely the crisis would fall upon the euro zone.

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And if share prices do fall further, or if demand in America slows abruptly for some other reason, effective remedial action is still possible: the Fed could cut interest rates (as it did, too much so as it turned out, after the stockmarket crash of 1987) or Congress could cut taxes.

ECONOMIST: Heading for meltdown? | The