Gas prices have been plunging lately. For consumers, that's great! It's more money in your pocket. 

Gas now averages $3.07 a gallon nationwide, down from $3.60 in June and $3.30 a year ago. That's billions of dollars of savings for U.S. households. 

But gasoline is one of the few products whose prices we vividly remember. Behavioral economist Daniel Ariely once explained:

For the several minutes that I stand at the pump, all I do is stare at the growing total on the meter -- there is nothing else to do. I have time to remember how much it cost a year ago, two years ago, and even six years ago. 

Gas may be cheaper today than it was a year or two ago, but I've heard several people recently say, "Sure, but I remember when it was $1.50 a gallon!" That nostalgia makes us think we're still paying a fortune at the pump. 

But several other things have changed lately that affect the real price of gasoline: 

  • The average car has a much better fuel economy today than it used to. 
  • The average American is driving less than they used to. 
  • Average nominal wages are higher today than they used to be. 

You have to adjust for all three improvements to show the true price of gas, and the real impact it has on our wallets. 

When you do, the real price of gas is lower today than it was a decade ago, and about the same as it was in the early 1990s:

Gasp

Source: Department of Transportation, Energy Information Agency, Bureau of Labor Statistics. The formula used to calculate this graph is: (average gas prices/average hourly wages of nonsupervisory workers) * (annual miles driven per capita/average MPG of passenger cars). 

One of the most important forces in economics is that people adapt. And that's what you're seeing here. 

Gas prices surged in the early 2000s, so auto companies started building more fuel-efficient cars, which consumers demanded (as did new regulations). 

Fuel-efficient cars used to be dinky little toys that you'd be embarrassed to drive. That's changing. GM (NYSE:GM) CEO Mary Barra commented last month: "The customer has that expectation. It's not an 'or', it's an 'and.' They're expecting to have winning vehicles, but also to have the fuel efficiency. It becomes a business priority." 

Consider: A 1999 Chevy Suburban got 18 miles per gallon and had 290 horsepower. A 2015 Suburban gets 23 miles per gallon with 355 horsepower. 

High gas prices also likely played a role in pushing families from the suburbs into the cities, where commutes are shorter. As Reuters reports: "In 2010, a total of 80.7 percent of Americans lived in urban areas, up from 79 percent in 2000. Conversely, 19.3 percent of the U.S. population lived in rural areas in 2010, down from 21 percent in 2000."

I'm not a fan of forecasts, because they're pretty much all wrong. But here goes: Over the next 20 years we'll see moderately higher gas prices combined with much better fuel economy. Taken together, this chart -- with all its adjustments -- won't look too much different two decades from now than it does today. 

"Intelligence is the ability to adapt to change," Stephen Hawking said. And we are. 

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Morgan Housel has no position in any stocks mentioned. The Motley Fool recommends General Motors, and has a disclosure policy.