Americans are a nation of procrastinators. Our tax returns prove it.

Last year, 21.5 million Americans waited until the last minute – or at least the last week – to submit their tax returns. That’s roughly one in seven filers, according to data from the Internal Revenue Service.

If anything, that count probably understates the number of people leaving it to the last minute. The figures are based on when the IRS received taxpayers’ forms, but the agency treats anything postmarked before the deadline as on-time. Last year, the IRS received nearly 6 million filings in the month after the April 15 filing deadline. (So far, this year’s filings are coming in at almost exactly the same rate as last year’s.)

Procrastinators get a few extra days this year. Friday is Emancipation Day in Washington, D.C., so tax returns aren’t due until Monday. And because Maine and Massachusetts celebrate Patriots Day on Monday, those two states’ residents get until Tuesday.

Still need more time? The IRS grants an automatic six-month extension to anyone who requests one by the normal filing deadline. Last year, nearly 13 million people asked for extensions, and many of them waited right up until the extended deadline of Oct. 15 to file. That’s the blip in October in the chart above.

On the other end of the spectrum are people who file their taxes as soon as the IRS starts accepting returns, usually in mid-January. Economically, that’s the smart move, at least for the roughly three-quarters of Americans who get a refund. A tax refund is an interest-free loan to the government; the sooner you file, the sooner you can get that money back.