Professors Richard Larrick and Jack Soll conducted tests to see whether the unit of MPG was giving people the wrong ideas. As it turns out, they were right.
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We've always used Miles Per Gallon as the unit for measuring the gas mileage and fuel efficiency of automobiles. Why? Sure, the numbers are fairly easy to work with, but just because it's easy doesn't mean we've found the best way to do it. With all the innovation going on with hybrids and making more fuel-efficient cars, now is the time to change the way we measure the fuel efficiency itself.
Duke University professors Richard Larrick and Jack Soll conducted tests to see whether the unit of MPG was giving people the wrong ideas. As it turns out, they were right; most people were thrown off by MPG : "for example, most people ranked an improvement from 34 to 50 mpg as saving more gas over 10,000 miles than an improvement from 18 to 28 mpg, even though the latter saves twice as much gas.
"These mistaken impressions were corrected, however, when participants were presented with fuel efficiency expressed in gallons used per 100 miles rather than mpg."
The New York Times wrote that "[Larrick and Soll] ran a series of experiments to show that the current standard of miles per gallon leads consumers to believe that fuel consumption is reduced at an even rate as efficiency improves. But that’s not the case.
The following graph plots Gallons Used Per 100 Miles vs. Miles Per Gallon between 10 and 60 Miles Per Gallon. Note that the relationship between fuel savings and MPG is not linear. Also note that changing from a 10mpg vehicle to a 20mpg vehicle (5 gallons saved per 100 miles) is five times more efficient than changing from a 34mpg vehicle to a 50mpg vehicle (1 gallon saved).
As professors Larrick and Soll found in their examination, many people have trouble understanding this. We should switch our system of units to GPM to avoid any confusion. Fuel efficiency would be rated with a single-digit number, the lower the better. When comparing two cars' GPM, all you would need to do is subtract one from the other. Wouldn't that be so much easier than a hyperbolic equation?
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