GBP/USD is down 7% on the month. We'll round up because we're being apocalyptic... according to outside investors, the UK economy lost 10% of it's value overnight.
As a point of reference, 7% of UK GDP (2.678T USD in 2013 [1]) is roughly 187B USD. UK M3 might be a better measure, about 2.44T GBP [2]. By that calculation, a 7% haircut comes out to about 236B USD if I did my conversions correctly.
The value of currency is not a measure of the value of the economy. CAD has lost 35% versus the dollar since 2011. But the Canadian economy has grown slightly more (in relative terms) than the US over that period.
And if we were to measure everything against Bitcoin since 2009...