According to news reports, the Obama administration is talking to
automakers about raising the Corporate Average Fuel Economy standard for
passenger cars to 56.2 miles per gallon by 2025, more than double the
27.5 MPG in force for the 20 years up to 2010. Economists, even those
like myself who favor policies to reduce fuel use, have argued that CAFE
standards are a bad idea. Has anything changed to make stricter fuel
economy standards look better now than in the past?
The
fundamental problem with CAFE standards is that they attack the negative
externalities of motor fuel use (pollution, national security concerns,
highway congestion, accidents) only partially and indirectly. As a
result, the cost of achieving a given reduction in fuel use via CAFE
standards is higher than it would be if the same result were achieved
more directly through an increase in the federal gasoline tax.
To
understand why, we need to consider the various ways consumers can cut
back on fuel use. In the short run, they they can buy an efficient
hybrid instead of a gas-guzzling SUV, they can reduce discretionary
driving, or they can shift some trips from their Ford F-250 to their
Honda, if they happen to have one of each in the driveway. Given more
time to adjust, they can make work and lifestyle changes like moving
closer to public transportation, work and shopping, changing jobs, or
working at home.
Higher fuel prices directly affect all of these
choices. They encourage people to make whatever marginal adjustments
best suit their circumstances. A
recent New York Times article gave these examples of how people were reacting as gasoline approached $4 per gallon in May, 2011:
- An
upstate New York customer relations manager moved to a new apartment
that cut her daily commute from 50 miles to 8 miles. She preferred that
to trading her beloved truck for a low-mileage vehicle.
- Traffic on San Francisco's bridges fell while ridership on buses and ferries rose.
- New York-based Topical BioMedics switched to cloud computing to make it more convenient for employees to work from home.
- A
Los Angeles hair products business found more workers taking advantage
of a long-standing offer of a 20-cent per mile bonus for car pooling.
The
problem with higher CAFE standards is that they encourage fuel saving
only with regard to the choice of what car to buy. Once a consumer buys a
low-mileage vehicle, the cost of driving and extra mile goes down,
thereby reducing the incentive for fuel-saving measures like moving
closer to work, working at home, riding the bus to work, or
consolidating errands.
The tendency of more fuel-efficient
vehicles to induce additional driving is known as the "rebound effect."
For example, suppose that the elasticity of demand for driving with
respect to fuel-cost per mile is -0.3. That means a 10% increase in fuel
efficiency would cause a 3 percent increase in driving. The increased
miles driven would partly offset the increase in miles per gallon, so
that total fuel consumption would decrease by only about 7%.
Even
taking the rebound effect into account, higher CAFE standards are still
somewhat helpful in reducing those externalities that are proportional
to the quantities of fuel consumed, including externalities of pollution
and national security. However, the rebound effect causes an absolute
increase in those externalities that are proportional to miles driven,
including road congestion and traffic accidents. It also increases the
cost of road maintenance, because the wear and tear from more miles
driven is only partly offset by the lower average weight of high-mileage
vehicles.
The very fuel-saving strategies that CAFE standards
discourage, like moving closer to work or consolidating errands, are
often the ones that have the lowest costs. That is why the total cost of
reaching a given national fuel-saving target will be greater when
achieved through CAFE standards than when induced by an increase in fuel
taxes. A
2004 study from the Congressional Budget Office concluded
that an increase in the federal gasoline tax would achieve a given
reduction in fuel economy at a cost 27 percent less than that of an
equivalent tightening of CAFE standards. Furthermore, its effects would
be felt more quickly, because they would not have to wait for the
gradual turnover of the national motor vehicle fleet. Over the 14-year
time horizon of the CBO study, the gas tax increase would save 42
percent more total fuel.
The variable most critical to the size of
the rebound effect, and therefore to the relative merits of CAFE
standards vs. fuel taxes, is the price-elasticity of demand for fuel.
The less elastic is demand, the stronger is the case for CAFE standards;
the more elastic, the larger the rebound effect and the stronger the
case for raising fuel taxes. So what do we know about price elasticity?
Of all the many elasticity studies, the most widely cited is a
1996 meta-analysis by Molly Espey.
She concluded that the best estimate for the price elasticity of
gasoline demand was -0.26 in the short run and -0.58 in the long run.
Those estimates strongly undermine the case for CAFE standards. However,
Espey's results, which are based on data from 1936 through 1986, have
been challenged by more recent estimates that show a decrease in
elasticity in the early years of the 21st century.
In particular, a
2006 NBER working paper
by Jonathan E. Hughes, Christopher R. Knittel, and Daniel Sperling
found evidence that the short-run price elasticity of gasoline for the
period 2001-2006 had fallen to a range of -0.034 to -0.077. That finding
would seem to strengthen the case for higher CAFE standards.
The
authors of the NBER study suggest several reasons that the elasticity of
demand for fuel may have fallen during the period studied. One is that
the real price of gasoline and its share in household budgets was below
its historical average in those years. A second possible reason is that
suburban sprawl and longer commuting distances meant that a lower
proportion of all driving was discretionary. A third explanation was
that after more than a decade in which CAFE standards had remained
unchanged at 27.5 MPG, there were fewer opportunities for saving fuel by
trading in an older car for a new one or shifting driving from one car
to another within the family fleet.
But not so fast. Still more
recent studies seem to show that the factors at work in 2001-2006 were
temporary, and that after hitting a low, elasticity is on the rise
again. A study by
Todd Litman of the Victoria Transport Policy Institute,
released just last month, provides a comprehensive review of the
literature. His conclusion is that long-run fuel price elasticities have
returned to a range of -0.4 to -0.8. In Litman's view, the rebound of
the rebound effect (as he puts it) has occurred in part because rising
fuel prices and stagnating incomes have once more increased the share of
fuel costs in consumer budgets. Also, as a larger share of the
population reaches retirement, a higher percentage of driving becomes
discretionary, and therefore more sensitive to fuel prices.
It is
worth noting that much of the observed variation in fuel prices on which
the elasticity studies draw are market-driven, and therefore expected
by consumers to be transitory. Elasticity is not only likely to be
higher in the long run than in the short run, but also higher in
response to changes in fuel prices that are expected to be permanent,
such as those that would result from tax increases. The expectation
effect would be even greater under a variable, price-smoothing oil tax
of the type discussed in
this earlier post.
Such a tax would put a permanent floor under retail gasoline prices,
providing maximum incentive to make the behavioral changes needed for
long-run fuel economy. The effectiveness of higher fuel prices in
mitigating externalities of automobile use would greater still if they
were backed up by modern, time-of-day pricing policies for road use and
parking, as well.
To be sure, not everyone will be convinced by
elasticity studies. They are just numbers. Some people will continue to
believe that prices have no effect on driving behavior, that people will
just drive whatever and wherever they want regardless. Here is a
picture, then, that is worth a thousand meta-analyses. Taken from the
Litman study cited above, it shows a convincingly tight relationship
between fuel prices and fuel use across OECD countries. Can it really be
just coincidence that the United States, with the lowest fuel prices,
also has the highest fuel consumption?

All
this leaves one last question. If CAFE standards are such a bad idea,
why do they remain so popular? If you are an economist, choosing higher
fuel taxes over CAFE standards looks like a no-brainer, but if you are a
politician, fuel taxes have an obvious drawback. Fuel taxes make the
cost of reducing consumption highly visible. You see the big
dollars-per-gallon number right there in front of you every time you
drive up to the pump. CAFE standards, in contrast, hide the cost. You
pay the price of a higher-mileage car only when you buy a new one, and
even then, the part of the price attributable to the mileage-enhancing
features is not broken out as a separate item on the sticker. You may
notice that your new car costs more than your old one did, but there are
lots of other reasons for that besides fuel economy.
It is a classic case of the
TANSTAAFL principle—There
Ain't No Such Thing As A Free Lunch. If you try to make something look
like it’s free, it only ends up costing more in the long run. If you are
a politician, you may well prefer a big hidden cost to a small visible
cost. If you're a friend of the environment, you should know better.
Originally posted at Economonitor.com