I read this post by Greg Mankiw awhile ago and found part of it amusing. The part I found amusing was his use of Eugene Volokh’s argument against slippery slopes.
If you accepted this slippery slope argument, then you’d end up accepting the next one and then the next one until you eventually slip down the slope to rejecting all government power (or all change from the status quo), and thus “break down every useful institution of man.”
What I find amusing is that the Volokh quote that Mankiw selected resorts to a slippery slope argument to argue against slippery slope arguments. And what is more, we have plenty of examples of where there is a slippery slope when it comes to government power and its aquisition of more and more power along any given “gradient”. Anyone want a nice cup of Kelo? Many of the blawgs I read about Kelo basically had responses like, “What is the big deal, this is the way eminent domain law has been moving for the last several decades.” How about Radley Balko’s work with SWAT units. Initially they were created to deal with extreme emergencies such as a crazed sniper on a building, a multiple hostage situation with multiple bad guys, terrorists, etc. Now, they SWAT teams are used to routinely serve drug warrants on non-violent offenders and the difference between knock-and-announce and no-knock is virtually nothing. Another example is intellectual property laws. When you look at these laws over time they have grown to cover more and more things.
I think Prof. Mankiw also makes a mistake when he rights,
Ultimately, policy is set by the median voter. When smart economists like David Friedman reject the first-best moderate policy to advocate the do-nothing position, he loses credibility among moderates, and that makes it easier for climate-change extremists to convince the median voter that we need to do something extreme.
Sure, in a perfect world, rejecting the “moderate first best policies” is not very smart. However, we don’t live in a perfect world, we live in the real world and “moderate first best policies” are about as common as perfectly competitive markets. And, it isn’t clear that the median voter decides these policies. There are some problems with the median voter theorem. First off, it the givens for the theorem is that the decision has only a single dimension. Most elections in this country are multi-dimensional and cover such topics as taxes, health care, gay marriage, abortion, foreign policy, gun ownership, education, civil rights and so forth. Second, it isn’t clear that the median voter always has to decide the outcome. The Median voter decides the outcome if and only if the distribution of policy preferences is single peaked (think of a bell curve here). If there is more than one peak, or no peak at all, then it isn’t clear that the median voter will be the deciding voter. And last but not least, there is nothing in the median voter theorem that argues the median voter’s policy preference is the optimal policy. In fact, this can only be asserted if and only if the distribution of policy preferences is symmetrical about the median.
Now all that being said, I still think that Prof. Mankiw’s notion of a gasoline tax is a good one. His list of reasons for such a tax can be found here and while each one by itself may not be persuasive taken as a whole it is a pretty good argument. Do I think it will be put into effect? No. Why? Because while all the reasons for such a tax are good one’s the idea of raising taxes is very unpopular, especially on a commodity that has already seen its price go up substantial over the past few years.
