When I link to my post where I propose a complicated Fuel Efficiency Payment--equal to the inverse of a cars fuel efficiency multiplied by total miles traveled--to encourage/incentivize/force drivers to internalize the long list of externalities associated with driving, I get comments along these lines:
No one ever mentions how easy it would be to circumvent this tax. Your mileage gets checked once per year? Just disconnect the odometer for most of the time. Or are we going to pay to retrofit all cars with "tamper proof" odometers that will soon be proven not-so-tamper-proof-after-all? Saving thousands of dollars per year in a tax is an awfully strong economic incentive for millions of very smart people to figure out how to game this silly system.
Unfortunately, I think I made the original post too long and comments like this illustrate that no one reads to the end when I'm long winded. So here's the punchline (highlighted in the hopes that it will get attention): The proposed Fuel Efficiency Payment is ridiculously complicated and mathematically identical to the much simpler $1/gallon gas tax that some (many?) economists support.
For those demanding readers who want proof, here you go. With a gas tax, the total gas taxes paid is equal to the gas tax per gallon multiplied by the number of gallons consumed. The number of gallons consumed can be found by dividing the total miles traveled by miles per gallon (mpg). For example, if a car that travels 10,000 miles gets 20 mpg, that car will require 500 gallons of gas (10,000/20). The total gas taxes paid by that driver is the per gallon tax multiplied by gallons consumed. So if the gas tax is $1, the total taxes paid can be found by dividing miles driven by the mpg (as proposed in the complicated fuel efficiency payment) OR by multiply the total gallons consumed by $1. The latter seems much simpler.
So here's the point: with a per gallon gas tax, total taxes paid will increase with miles driven and decrease as fuel efficiency increases. The gas tax creates the incentive to Drive Less! and drive more efficiently.
And a gas tax can't be manipulated as easily.
It is also work noting that a driving tax and a fuel efficiency payment/gas tax are not equivalent. A driving tax is a flat rate tax per mile driven for all cars. The driving tax creates no incentive to increase fuel efficiency (and possibly a disincentive) since increases in fuel efficiency will not reduce miles driven (and may increase them).