The United States recently hit an alarming milestone.
The federal debt crossed $40 trillion.
It's an eye-popping stat,
and it's left a lot of people wondering,
how is the US able to borrow so much money?
Well, one reason is because everybody wants our US dollars.
You can travel almost anywhere in the world and pull out a $100 bill.
Those Benjamins have been a symbol of prosperity and stability for decades.
For the last 80 years,
banks and other countries have kept loads of dollars on hand
because the US dollar is the most traded currency in the world.
How did that happen,
and could the days of dollar dominance be coming to an end?
From the BBC, I'm Asma Khalid in Washington, D.C.
And today on The Global Story, has the US dollar peaked?
To help us make sense of this incredibly complicated story,
we decided to call up Ken Rogoff because he seems like just the man to explain it all.
He was the former chief economist at the IMF, the International Monetary Fund,
and is now an economics professor at Harvard who's written a book called Our Dollar, Your Problem,
all about the US dollar's dominance.