Hello and welcome to More or Less on the BBC World Service, where you'll weekly guide

to the numbers in the news and in life. And I'm Charlotte McDonald. Our email inbox is

often overflowing here at More or Less. But don't have that put you off emailing us at

more or less at bbc.co.uk. We might just be able to answer your question as we're about

to do with this brief and to the point message from loyal listener Andrew.

Subject. US National Debt. Is 31.4 trillion dollars a big number?

31.4 trillion dollars. That was the level of US National Debt earlier this month on June 12th

when Andrew sent his email. By June 23rd, the date we made this programme, Debt had actually

breached the 32 trillion mark. What's a few hundred billion between friends? Either way,

32 trillion sort of looks and feels a bit like a big number. It is 32 million millions

after all. If you're finding it all very hard to get your head around, think of it like

this. A million seconds is 12 days. A billion seconds is 31 years. And a trillion seconds

is 31,688 years. But is 32 trillion dollars a big number in the context of National Debt?

Betsy Stevenson, professor of economics and public policy at the University of Michigan.

She says the most useful way of getting an idea of the scale of what a country owes is

to measure the debt against a country's economic output per year. Otherwise known as GDP.

When we hear a number like 32 trillion, it might as well be 32-gajillion because nobody

knows what that means. So how do we make sense of it? And I think that's got to be the

starting places to figure out how to scale such a big number to be able to think about whether

that's a lot of debt or not a lot of debt. And one of the big tricks is you got to scale

it relative to something you understand. So when it comes to debt, the standard thing to do

is to scale it relative to GDP. And if you look at US debt relative to GDP, otherwise known as

...