My friend Kevin sent me this link at bunnie's blog all about how replacing an inefficient car with a slightly less inefficient one is much more efficient than replacing an efficient car with an even more efficient one. (You gotta stop and read the entry, but for a better explanation of the usefulness of "gallons per mile," see Science Daily.)
He or she (not sure who bunnie is) does a bunch of math and produces a graph and everything, until you're bamboozled into thinking that bunnie is way more wise than anyone you've ever met. I was about to hand over all my worldly goods to the bunnie god until I read:
"There are some important policy implications of this. Relatively small MPG improvements in the most gas-hungry vehicles pay off greater than larger improvements in already efficient cars (hence, it does make sense to offer tax breaks for modest improvements in SUVs versus tax breaks for hybrids, which typically replace already gas-efficient sedans)."
I'm going to skip right over what hybrids "typically replace," despite the fact that bunnie doesn't bother to back up this statement. The whole concept of "replacing" a car only makes sense from the perspective of an individual owner, not from the point of view of the car. (Gettin' all Einsteinian on you there.)
A car has the same lifespan -- for example, about 30 years -- whether it's owned by one or one hundred people. So if someone replaces an SUV, that SUV is still out there, polluting at large, under the auspices of a different driver. Public policy (unless it's really radical and calls for the destruction of existing cars) can't control the old car you're "replacing." But the new car you buy will hang around for about 30 years, too. So do you encourage people to buy a new, slightly less inefficient SUV? Or a new, more efficient hybrid?
The answer depends on what people's buying patterns are. Gas mileage and price are two considerations, but there are lots of others: safety, size, utility, looks, penis size or lack thereof... so a price adjustment (via a tax break) has to outweigh a bunch of unrelated concerns.
For example, I could drive a bike if it weren't for my dog. But all that communing with nature we do requires copious CO2 emissions. If I were to buy a new car, I'd get the most fuel-efficient one I could afford that I could stuff my dog into. Are we still talking about tax breaks? Or are we now talking about how wide (or narrow) the selection of fuel-efficient cars is?
SUV drivers are always talking about things like safety, having a car mass that can outsmash your car mass, seeing over the less important cars, fitting their over-privileged IVF children into the back, and finding time to vote Republican. So it's true that science has yet to discover the tax break that would get them to switch over to a Prius.
Does that mean we should offer them a tax break for a slightly less obnoxious SUV? Or does it mean that we should offer a tax break for whatever level of fuel efficiency we want hanging around for the next 30 years, and let the car manufacturers figure out how to design that level into an SUV? (Maybe "let" is too passive a verb -- manufacturers can be offered incentives as well.)
If you really can't make the gas guzzlers much more efficient, then sure, maybe tax breaks are the way to go. Making that incentive hinge on which car you're replacing is a preposterous complicated paperwork mess, rife with opportunities to cheat. And only relevant if we want to make sure to encourage the people of the future to keep exchanging up, so that the gas guzzlers are slowly deprecated over time. (Due to consumer pressure on manufacturers to keep turning out more efficient, tax-break worthy cars -- so that each year the whole fleet is slightly better than the previous year.)
But you could make the amount of the tax break dependent on the fuel efficiency of the new car. For example, you could offer a tax break on SUV A (that gets 30 miles a gallon), a smaller one on SUV B (that gets 15 miles a gallon), and none on SUV C (that gets 10 miles a gallon).
Although...if buyers were educated that buying B instead of C saves them about 350 gallons a year, do we really need the tax breaks? Seems like all we'd need to do is point out that SUV B also comes with a Homer Simpson-sized beverage holder.