The U.S. national debt has increased by more than half a trillion dollars in less than six months, amid predictions that the U.S. is on the verge of returning to another explosion in government borrowing.

The debt rose to an all-time high of $21.4 trillion on Thursday, according to government data posted Friday. That’s more than $500 billion above the $20.88 trillion seen March 7, just a bit more than five months ago.