He found that the birds are, for a substantial part of the wingbeat cycle, forced into the incline.

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We saw this vicious cycle in junk bonds after Mike Milken was forced to suspend his activities as the market maker for the junk bond market.

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Meantime, the oldest coal units built in the middle 1900s are being forced to retire and they are getting replaced with combined-cycle natural gas plants that are both more efficient and cleaner.

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The trouble is, if the economy reaches capacity sooner than expected, or the economic cycle turns down as one day it will the government may find itself forced to put up taxes or cut spending just when life is becoming more painful throughout the economy.

ECONOMIST: The economy