When you’re fumbling through airport security — putting your shoes and belt back on, finding your glasses again, stowing your laptop back in its bag — do you make every effort to make sure you’re not leaving anything behind in the plastic bins? Maybe you’re not doing as thorough a job as you think, because someone is leaving hundreds of thousands of dollars in loose change behind every year.

USA Today looks at the “unintentional tips” that travelers are unwittingly providing to the TSA when they leave money behind at the security checkpoints.

The law allows for the TSA to collect and keep the unclaimed money lost at checkpoints, most of it in the form of loose change left behind in bins from travelers who hastily empty their pockets.

While it might just be a penny here and a dollar there, it adds up. In 2015 alone, the TSA collected nearly $766,000 from travelers who either didn’t notice or didn’t care that they were leaving behind some pocket change.

That’s nearly double the $383,000 collected in 2008. Since then, the yearly total has increased almost each year (with the exception of a one-off dip in 2010), resulting in a total of more than $4.32 million collected over that eight-year period.

What happens to all this money?

“Receipts of unclaimed money are deposited into a Special Fund account so that the resources can be tracked easily and subsequently expended,” the TSA explained in a statement to USA Today.

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