NEW YORK (CNNMoney.com) -- You heard about the growing problem of Americans not saving enough for retirement? Check this out.
Nearly half of respondents to a recent survey said they lose track of how they spend their pocket cash - on average, more than $2,000 a year.
The study, released this week, was commissioned by Visa in an effort to help make the case for debit cards as a good way to manage money.
"It's understandable that consumers would lose track of some cash over the course of a week, but we were surprised by how much cash goes unaccounted for at the end of a week - a dollar here and a dollar there definitely adds up," said Wayne Best, Visa's chief economist, in a statement.
The survey asked 2,036 respondents to estimate their "mystery spending," or money they couldn't keep track of. Of the respondents, 48 percent said they couldn't account for an average of $2,340 a year. At the extreme end of the spectrum were 7 percent who said they lost track of more than $100 per week, or $5,000 a year.
Respondents 34 and under are the biggest offenders.
Men in this group lost track of an average of $59 a week, or $3,078 per year, with 56 percent of them reporting that they blew the cash during a night out. Young women spent $52 in unaccounted-for cash a week, or $2,709 per year. And 67 percent blamed shopping trips. 
