Jevons Paradox (1)

Fuel efficiency vehicles stimulate MORE fuel consumption.

Since 1970 greenouse gas emissions in the transportation sector have more than doubled. This is the case despite the development of new and more fuel efficient technologies. This counter-intuitive effect is called the Jevons Paradox. For the environmentally concerned this may sounds phony. But this is the way it is. The more efficient our vehicles are, the more GHG emissions.

For the last 40 years vehicles have undertaken major improvements in fuel efficiency. Miles per gallon haven almost doubled (2) since 1970, from 13.7 mpg in 1970 to 23.0 mpg in 2010. See figure below.

 
Therefore it would sound reasonable to expect a reduction in energy consumption. This is not the case. Total Energy Consumption has almost doubled in Transportation in the US since 1970 (3). See figure below.

Where did our logic go wrong?
Total fuel consumption in transportation is driven by the following simple formula:

TFC = NV x NM x MPG

Key:
TFC = Total fuel Consumption (within a year) in transportation
NV = Number of vehicles. This includes quads, motorbikes, jet-skis, dune buggies, sea-planes, etc.
NM = Number of miles per year, on average, made by each vehicle
MPG = Miles per gallon: number of miles made by a vehicle, on average, with a single gallon.
Results don’t turn out as expected because we are focusing in one single factor only, MPG, even among the environmentally concerned. This is wrong. What counts is not how much gas a vehicle burns in one mile, but how much gas is burned by all vehicles throughout the US. In other words, what really counts is TFC.
In the above equation NV has increased manifolds. The number of vehicles is increasing due to an increase in the US population, but there are other economic factors as well. As the society is developing more efficient technologies, it is also becoming more productive. As a result, average overall wealth is rising, generating an increase in auto ownership. But that’s not all, since 1970 new forms of leisure transportation, quads, motorbikes, jet-skis, seaplanes, motorboats, etc. are being incorporated into the system as well.
The number of miles per year, NM, is also increasing. People are moving further away from the city centers; there is an increase in leisure transportation, and there is also an important shift to air travel. Fuel efficiency improvement in aviation has been even more impressive than in the auto industry. As a result, this mode of transportation is becoming cheaper and therefore more popular. The problem is that air transportation is adding many, many more miles into the system since airplanes bring us to further away destinations.
Worldwide energy consumption in the transportation sector is predicted to continue increasing (4). As we have seen, future fuel efficiency technologies will make things worse unless… we learn to move less.

(1)    In 1865 William Jevons studied the problem of depletion of England's coal deposits. In his book “The Coal Question”, he predicted that improvements in fuel efficiency increase, rather than decrease, fuel use.
(2)    Average vehicles in use. Source U.S. Bureau of Transportation Statistics
(3)    Quadrillion BTU. Source US Energy Information Administration
(4)    US Energy Information Administration. Report DOE/EIA-0484(2011)

2 comments:

  1. At the same time, some people are already arguing that the US may be close to reaching peak car and peak mileage:

    http://deepblue.lib.umich.edu/bitstream/handle/2027.42/98098/102947.pdf

    http://deepblue.lib.umich.edu/bitstream/handle/2027.42/98982/102950.pdf

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    Replies
    1. Thanks for your comment. You are right. Road transportation fuel consumption is reaching a plateau in developed countries. Just because our vehicles are more fuel efficient it does not mean we will drive more often to work. After all, there are 24 hours a day maximum and we want to enjoy life too.
      What is happening is that fuel efficiency is allowing people to switch to aviation. This is the case since air transport is becoming cheaper. That allows us to do many more miles, and therefore more fuel consumption. You can find some EU statistics in the following site:
      http://goo.gl/nPwiwg
      Increasing wealth is also allowing people to burn fuel in their leisure time. There are many more jet-skis, quads, motor boats, private planes than before. As an anecdote, extremely wealthy people like John Travolta can afford flying a B707 for fun!!!
      Thanks again for commenting.

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