Why the New CAFE Standards Are Good — But Hardly the Best Climate Policy

By / 4.5.2010

Cars and trucks sold in the U.S. will have to be a little more efficient, according to new Corporate Average Fuel Economy (CAFE) standards released last week by the Environmental Protection Agency (EPA) and the Department of Transportation.

The new standards are largely a product of a compromise between states, the federal government and auto manufacturers last year. (Is it still a compromise if one party—the feds—owns a big chunk of another—the U.S. auto industry—and has Supremacy Clause powers over another—the states? Just asking.) They are also the end product of the Supreme Court’s Massachusetts v. EPA decision requiring the EPA to address impacts of greenhouse gases under the Clean Air Act. The requirements appear relatively modest: the existing requirement of 35 mpg fleet average fuel economy by 2020 is moved up to 2016 and increased by 0.5 mpg.

That apparently small change can have a big impact when you consider how many cars and trucks there are in the U.S. and how long those vehicles will remain on the road. The EPA claims that the standards will reduce greenhouse gas emissions by 960 million metric tons and cut U.S. auto emissions by 21 percent over business as usual by 2030. The EPA also estimates that increased up-front vehicle costs of about $1,000 will be offset over the course of each vehicle’s life by reduced fuel costs, resulting in a savings of about $3,000.

That’s good news for the environment, and good news for consumers, right? The auto industry is (at least for now) OK with the new standards, and the environmental community is generally happy as well. I think the positive spin is broadly correct — we’re better off with stricter CAFE standards than we would be without them.

That said, I’m skeptical about the size of the benefits estimated by the EPA. Performance standards, and in particular efficiency standards, are flawed policy tools — emissions benefits may be lower, and costs higher, than with the best alternative: a carbon price.

The largest problem with efficiency standards is that they encourage increased use of whatever is being made more efficient. If your car is more efficient, it’s cheaper to drive it, and you’ll probably do so more often (and for longer distances). You might even move farther away from work or make other choices that increase your fuel consumption (but not your cost — remember, you’re more efficient now). This is great for you since you get increased utility from driving more, but your vehicle emissions won’t go down as much. Even if you “save” more money over the life of the car, the added cost per unit of emissions reduction goes up. Other social costs, like traffic congestion and increased risk of accidents, go up as well. This is called the “rebound effect,” and estimating its size is the subject of significant research among economists.

The EPA is aware of this effect and, as you might expect from an 837-page rule (with a 475-page regulatory impact analysis and 215-page technical support document), accounted for it in its analysis. Both the EPA estimates of emissions reductions and of costs to consumers assume that owners of new, more efficient vehicles will drive more. Good job by the EPA, right? Maybe.

Digging deeper suggests that while the EPA is accounting for the rebound effect, it might be underestimating it. The EPA assumes the effect will be 10 percent — that is, increased driving will erase 10 percent of the emissions reductions that would otherwise be achieved. This estimate, the EPA admits, is lower than that suggested by most studies of the effect for vehicle efficiency standards in the U.S. These studies give estimates from seven percent to 75 percent, with the average around 22 percent — more than double the 10 percent the EPA chose. The EPA bases its choice on other studies that suggest that the effect declines over time and then projects that trend into the future. It’s possible the EPA is right here (they are relying in part on the most recent and well-regarded work on the subject), but it still seems like a relatively optimistic estimate. Because of this, I think it’s more likely that the EPA will have overestimated the benefits of the new standards than underestimated them.*

The EPA’s analysis has other limitations as well. For example, fuel prices are projected to increase in the future due to rising global demand and other factors. This will lead to demand for more fuel-efficient cars independent of any standards, possibly making CAFE requirements superfluous. Emissions would still go down, but CAFE standards might not deserve the credit.

For me, the worst part isn’t that the EPA might have overplayed an obscure (but important) assumption, or taken credit for something that might happen anyway. Even if they haven’t done either of these things, none of this is necessary. Pricing carbon, whether through an economy-wide cap-and-trade system, a transportation-sector only cap, or (hide the children) a higher gasoline tax, could achieve emissions gains without these perverse effects and estimation problems. These policies would increase the cost of gas — which is the point. If your reason for buying a more efficient car is a higher fuel price, there’s no incentive to drive more — there would be no rebound effect. In fact, there is a powerful incentive to drive less, reducing carbon emissions even further and giving other benefits: less congestion, fewer accidents, better air quality, etc. A gas tax or trading scheme would also be simpler, easier to administer and more transparent. It need not even hurt consumers: the revenues from permit auctions or taxes can be returned to households through lower taxes elsewhere, rebates or investments in public goods.

The reason CAFE standards, with all their problems, are and have long been our only policy option for controlling vehicle emissions has nothing to do with efficiency or good government — it’s politics. It’s not politically possible (or politicians think it’s not politically possible) to support a policy that increases prices at the pump. Instead, we hide costs in suboptimal and inefficient programs like CAFE. While it’s true that our cities and in some ways our society are built around driving, often long distances, that doesn’t mean we should hide the costs of those choices, or use second-rate policy tools because we can’t handle the truth. The politics behind CAFE are a shame, whatever benefits last week’s regulations will have.

* If you’re interested in the EPA’s decisionmaking process on the rebound effect, it’s candidly explained in Section 4.2.4 of the Technical Support Document.

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