If a US$ doesn't buy the same bundle of goods and services as it used to, and another currency, say the &euro, better retains its ability to buy a bundle of goods and services, the € will rise in the €/US$-PPP.

The problem is rather the time lag ... market rates are available on an ongoing basis, and trade-weighted exchanged rates at reasonably high frequency, even if not daily ... but it'll be sometime in 2009 that we have the estimates for 2008 PPP exchange rates.

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.