America’s debt now tops $16 trillion, and the meter never stops running. The national debt increases by about $35 million an hour, and around $2 billion every 24 hours.

As the country’s debt skyrockets, politicians and pundits are debating how to get it under control. If nothing is done, we could be $17 trillion in the hole later this year.

But for the first time in six years, the federal government said it would make a small down payment on the national debt – about $35 billion worth. They say higher tax receipts and recent spending cuts helped raise the money.

Which brings us to the topic of this Just Explain It.

What exactly is the debt? And how long would it take to pay it off?

First, here’s some history.

Before President Reagan took office, the national debt was $1 trillion. By the time President Clinton left the White House, it reached $5.6 trillion. Eight years later, the debt had almost doubled. And today it stands at $16.8 trillion.

So… where did all of this debt come from?

It’s more expensive now than ever before to send your son or daughter to college. So in order to stay attractive, some universities are beginning to offer tuition discounts. But providing more financial aid to incoming students doesn’t hide the fact that college costs are still very high.

Out-of-state full-time students who attended public four-year colleges felt it in their wallets. On average they paid almost $22,000 in tuition and fees this school year. In-state undergrads did a little better. They shelled out just over $8,600.

According to the College Board, in-state students faced an average tuition increase of $400 from last year. On top of that, room and board charges jumped by $325.

Related: Only 150 of 3500 U.S. Colleges Are Worth the Investment: Former Secretary of Education

But, a recent National Association of College and University Business Officers survey found that last fall many colleges offered an average of 45% off tuition for incoming freshman. That’s more than