** MMT is the new supply-side economics
Forty years ago, some economists started from an uncontroversial (but important) result: a lower tax rate raises the tax base, so revenues won't fall as much. But then they ran with it, predicting tax rate cuts could raise revenues.

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The 80s supply-siders went to the limit and came up with a motto: lower taxes will lower deficits as a norm, not an exception. Many economists shouted this was backwards. It was an implausible limit case. Textbooks called them "charlatans and cranks" or "silly".
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In 80s debates, supply-siders would often fall back to "you don't understand me", repeating "Laffer curve!" endlessly, or stating vacuous accounting identities about how the government collect taxes. Their extreme prediction was repeatedly proven wrong by theory and data.
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But they had popular hero figures (Laffer, Moore), and an eager political audience that would use any argument to cut taxes. Eventually, they inspired new good research, and helped in swinging the pendulum of policy debates to include some valid supply considerations.
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Yet, supply-side economic ideas also contributed to a massive rise in US public debt in the last 40 years. Right-wing governments became as prone to have large public deficits as left-wing governments, in the pursuit of cuts in taxes.
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