What happened to big savings at the gas pump?

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Some big savings at the pump seem to have gone missing.

The plunge in gasoline prices has generated a windfall for American drivers. But so far, there's little evidence those savings are producing a widely anticipated boost in consumer spending.

So where is all that money going?

There's no question the sharp drop in pump prices since last summer means a much smaller bite out of consumers' wallets. Though fuel prices have bumped up a bit, they're still some 30 percent lower than the five-year average cost.

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Even though prices didn't fall until late last year, Americans saved some $14 billion on gasoline last year, or an average $115 per driver, according to estimates from AAA. The group figures if pump prices stay tame, those savings could amount to as much as $75 billion this year.

That kind of saving—if consumers spend it elsewhere—could provide a powerful boost to the U.S. economy, much like a tax cut. But, so far, that spending boost isn't showing up in the data.

The latest read from the Commerce Department showed that retail sales in January barely budged after dropping in December. Those figures are echoed in separate government data on overall spending. While outlays on energy-related goods and services plunged in December and January, total personal spending on goods and services also weakened.

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Some consumers may be betting that the drop in pump prices is only temporary, a view likely reinforced by the bounce in prices last month.

"All the confidence gauges are now giving back ground as the novelty of lower gasoline prices wears off," said Action Economics' chief economist, Michael Englund, in a recent note.

For now, many drivers are apparently socking away their savings to build up a reserve for their household budget. Americans put away some $725 billion in January, pushing the savings rate to 5.5 percent of income from 4.5 percent in November.

Those savings also reflect the wide differences in spending on gasoline at different levels of income; lower-income households generate much less savings on gasoline than the wealthiest consumers, who can afford to save more.

While the average household spent about $2,600 on gasoline in 2013, the latest figures available from the government, those in the lowest 20 percent spent just $1,231 a year on fuel while the top 20 percent spent $4,071—or more than three times as much.

Even if gasoline prices stabilize at lower levels, and consumers begin spending the difference, the impact may be less than initial forecasts suggest.

For starters, while a typical consumer might save between $500 and $800 this year, those savings don't come in a lump sum right away, notes Wells Fargo senior economist Mark Vitner.

"On a weekly basis, the savings work out to between $10 and $15, which is meaningful for lower- and middle-income households, but not enough to finance a spending spree, particularly right off the bat," he said.

Vitner also notes that the impact of savings at the pump may be dampened by lower levels of overall gasoline consumption among people driving to work every day. Even though the job market has picked up in the last year, the labor force participation rate has fallen from 66.4 percent before the Great Recession to 62.9 percent today, he said.