I would bet that your fellow econ student became a Republican or Libertarian before convincing himself that higher taxes are provably inefficient. (Higher than what? Failing to have an answer to that proves irrationality.) Confusion induced by ideology is different from confusion induced by math.
Most Democratic academic economists agree with the claim that higher taxes are inefficient (“deadweight loss”). That inefficiency is the main cost of taxation, which must be balanced against the good that can be accomplished by the government using the revenue. (“Higher than what” you ask? Almost any increase in tax is inefficient. But DeLong and Mankiw certainly agree that a height tax is efficient.)
Well, the key is “what kind of taxes, and on what?”
Taxes that distort incentives away from the no-externality, no-taxes perfect competition equilibrium, do create econ-101-style inefficiency, but not all possible taxes distort incentives, not all possible taxes are on things that have no negative externalities, and not all markets are in a perfect competition equilibrium.
I would bet that your fellow econ student became a Republican or Libertarian before convincing himself that higher taxes are provably inefficient. (Higher than what? Failing to have an answer to that proves irrationality.) Confusion induced by ideology is different from confusion induced by math.
Most Democratic academic economists agree with the claim that higher taxes are inefficient (“deadweight loss”). That inefficiency is the main cost of taxation, which must be balanced against the good that can be accomplished by the government using the revenue. (“Higher than what” you ask? Almost any increase in tax is inefficient. But DeLong and Mankiw certainly agree that a height tax is efficient.)
Well, the key is “what kind of taxes, and on what?”
Taxes that distort incentives away from the no-externality, no-taxes perfect competition equilibrium, do create econ-101-style inefficiency, but not all possible taxes distort incentives, not all possible taxes are on things that have no negative externalities, and not all markets are in a perfect competition equilibrium.
In the real world, all else is never equal.