Macri's devaluation could have major impact on Argentine prices.

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3. That would be in nominal GDP per capita terms.

Even so, GDP will likely slip 2 to 3% this year in real terms - the first decline since 2002.

There's been much heated debate among economists over the last 30-plus years about the virtues of using nominal GDP and GDP per capita figures, since they don't take into account over or undervaluation of different currencies. Nor does it, of course, take into account average living conditions and income distribution.

About 30 years ago, then, the use of what's referred to as 'Purchasing Power Parity' became widely used to take into account the differences in costs between one country and the other.

A family of three in Argentina, for example, earning 1,000 dollars a month at the new rate of 14 pesos lives a decent, middle class life. One earning 2,000 dollars saves an average of 500 dollars a month, according to banking data. This is especially true if they live outside Buenos Aires.

It goes without saying that a family of three in the U.S. earning 2,000 a month is poor; one earning 1,000 would be indigent outright, without public assistance. In countries like the U.K. and Japan, income needs in dollars terms are even higher.