Megan wonders about the utility of a small gas tax:

It did take a lot of increase to change driving behavior, which is why in Europe, taxes can account for as much as 90% of the price of a liter of gas.   There's a plausible argument that a 40 cent tax won't do much to change driving habits.  But then, why have the 40 cent tax at all?  If you have a Pigovian tax that doesn't alter the production of the externality, cap and trade starts to look a lot less like controlling our carbon emissions, and a lot more like taxing people who aren't Ryan Avent and Megan McArdle to top up government revenue.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.