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Americans are spending more than $2 billion less a week on gas than this time last year

Gas prices keep dropping lower and lower, returning to what The Post's Steven Mufson calls "the old normal" — the price range that we saw before the last eight years, which were abnormally high, historically speaking. The drop has resulted in a lot of analysis and a lot of explanation, but one thing we hadn't seen was a clear answer to the most important question: How much money are we actually saving?

We'll cheat and give you the answer before we show our work. Compared to the first week of 2014, Americans are spending $2.4 billion less each week on gasoline. That's about $7.50 per week for every person in America.

How'd we get that figure? The Department of Energy's Energy Information Administration offers data on gasoline supply (which translates to gas consumption) and on gasoline prices. Meaning that we can figure this out.

Since 2000, here's what gas prices have done (without adjusting to 2014 dollars).

Gas prices are linked to a variety of factors and, as even a cursory visit to will demonstrate, vary pretty widely depending on where you are in the country. The EIA figure looks at national prices, which have dropped by $1.19 over the last year. The Midwest was at $1.95 a gallon as of Monday, while the West Coast was at $2.49. But the dollar-plus drop happened in both places.

Meanwhile, 8.8 million barrels of gasoline a day were supplied to retailers in the week ending Jan. 2, 2015, the most recent period for which data are available. Here's how that has fluctuated.

That's a huge amount of gasoline, of course, 8.8 million barrels. Each barrel contains 42 gallons, meaning that nearly 370 million gallons of gasoline were supplied each day of the week of Jan. 2. Each day!

The gasoline prices supplied by the EIA and the amount supplied don't overlap entirely, since the weeks don't match up. But it still offers a picture of how much we're spending each week. So the week of Jan. 2, prices were about $2.21 a gallon nationally. Meaning that we spent $5.7 billion that week on gasoline (since 370 million gallons were supplied each day for seven days).

That's a ton of money. But it's a lot less than we spent in the first week of January a year ago.

That week the United States spent about $8.1 billion on gasoline — $2.4 billion more. That's a huge, huge savings. (If you cheat and look at, say, May, the drop is about $4.3 billion, because people bought more gas.)

There are about 319 million people in the United States. That means Americans are paying about $7.50 less per person than a year ago. The good news for the other 318,999,999 Americans is that, if history is any guide, that $7.50 is being spent somewhere else. The Low Gas Price Stimulus is underway.

Correction: For some reason, I originally took the $7.50 and multiplied it by seven, despite the figure already being weekly. Thanks to commenter Ada Ada for pointing out the mistake.

Gasoline hasn't been this cheap since 2009. But why now, and how long will prices stay low? Here's what you need to know, in two minutes. (Video: Gillian Brockell/The Washington Post)