When introducing students to international currency exchange rates and purchasing power parity, The Economist's Big Mac Index is usually a nice discussion starter.
As useful (to me, at least), when teaching about the problems of making welfare comparisons, is Cox and Alm's Myths of Rich and Poor, where they reveal how many hours the average worker had to toil some years ago vs. now to buy, say, a three-pound chicken (and many other items they include).
Now it seems that these two expository devices have been brought together. The Economist (August 29) reports results of a UBS study that tabulates "How many minutes to earn the price of a Big Mac?".
Uh, oh. Chicago and Tokyo are at the top, where the least toil buys a Big Mac. If there are international food police (at Interpol?), what will they do with this? Tokyo residents are a lot slimmer than most Chicagoans.