Uses theory of purchasing-power parity (PPP)to compare exchange rate fluctuations based on a single global commodity
It's weakness seems to be that it revolves around the US Big Mac and is priced in dollars so it has been warped by the recent falls.
Here's another measure:
|| ||Size||Calories||% daily saturated fat||% daily cholestorol||% daily fibre||
||Big Mac®||7.8 oz (219 g)||560||52||26||15||