Aguanomics: Pigouvian taxes do NOT produce deadweight losses

David Zetland:

For my final exam question, I asked students to compare the pros and cons of cap and trade and Pigouvian taxes for reducing the negative externality from pollution. Many students gave useful answers, but many also made two big mistakes.

The first was to claim that an advantage was their propensity to reduce consumption (an excellent example of rewriting the question as the answer :).

The other was simultaneously frustrating and enlightening to me. Many students claimed that Pigouvian taxes created a deadweight loss, i.e., the tax would reduce surplus-generating activity.* That statement is true, in general, of fiscal taxes designed to generate revenue (e.g., income, property or expenditure taxes) that the government would spend elsewhere,** but it's NOT true of Pigouvian taxes that are designed to reduce behavior that generates harm that is not reflected in the price of the good being taxed, e.g., taxes on cigarettes to pay for additional health costs or taxes on fuels to reduce and/or ameliorate the costs of pollution.***

The trouble that my students encountered -- and many teachers of economics fail to clarify -- is that fiscal taxes distort prices to generate revenue while Pigouvian taxes correct prices to affect behavior. (We explore the tension between these two goals in this paper on groundwater taxes.)

Bottom Line: We use the same word ("tax") to refer to two different policy instruments. Fiscal taxes generate revenue with some reduction in efficiency; Pigouvian taxes generate revenue as they improve efficiency. (That's why they are called win-win, but don't tell that to the people creating the pollution!)

via www.aguanomics.com