Oil price fluctuations seem to preoccupy people less these days, maybe because they got used to higher prices or because other issues are hotter now. But remember how popular it was to call for the government, whatever the county, to reduce fuel taxes to ease the burden. Which bears the question whether this would be a good idea if you think harder about it.
Helmuth Cremer, Firouz Gahvari, and Norbert Ladoux did so and come to the conclusion that the fuel taxes should not move as much as the energy price. The reason is that the Pigovian motivation for imposing them, internalizing the externalities, has not changed, which would call for perfect smoothing. But this is to an important extend compensated by redistribution considerations as goods using energy are used by people of different incomes. In the end, a doubling of pre-tax energy prices lead to a post-tax increase of 64%. But that is only assuming that the tax was optimal to start with. In many countries it is currently much too low, thus the argument about reducing the tax in high price times is largely invalid, In fact, one should take advantage of reduction in world energy prices to increase the taxes, which would raise much needed money.