Turns out money really does burn a hole in our pockets.

In fact, according to a recent study by Visa USA, nearly half of all Americans "lose" $2,340 in cash each year. And 48% of those who use cash said they don't know what happened to more than one-third of it — or about $45 of every $120 spent in a typical week.

The money's not actually misplaced, just inexplicably frittered away. Wayne Best, senior vice president at Visa, calls it "mystery spending."

"You do spend the money, but you're not really sure where you spent it," he said. More could be spent during a night out on the town, for example, than you thought. Or maybe there's been a lot of ice-cream buying for the kids that you've forgotten about. Picking up a loaf of bread and a gallon of milk at the store throughout the week adds up too, he said.

About 62% of the 2,036 U.S. adults surveyed by telephone said that they "misplace" about $25 a week on "small cash purchases."

Many won't be surprised to hear this too: Men 34 years and younger are the biggest money sieves, losing track of $59 a week, or $3,078 a year. Their female counterparts drop an average of $52 a week, equal to about $2,709 a year, on miscellaneous spending.

Visa, of course, would like most Americans to use debit cards rather than cash and Best said of those who do, nearly two-thirds said their debit cards helped keep their mystery spending to a minimum; four out of five said it helps them track their spending.

Most financial planners, however, will tell spenders that the best way to track their spending is to, well, track their spending. How?

Keep a journal on where every penny and every dollar goes for at least a week to see how money is spent. Set goals on how money should be spent. Make a budget to accomplish those goals. Stick to it.

Copyright (c) 2007 MarketWatch, Inc.