In theory, a discretionary central bank could limit the quantity of money and achieve long-run price stability by controlling the growth of nominal final demand.

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"If you have a moment of instability, what happens is the muscles counteract by working to create stability -- in theory, " he said.

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Sanctions exist, in theory, in the stability and growth pact, which requires euro-area countries to keep deficits below 3% of GDP and government debt below 60% of GDP, but they have never been imposed.

ECONOMIST: Charlemagne