There is a middle class revolution happening in the largest economies in Central and South America, a counterbalance to the terrible news coming out of Europe



Shoppers carry an electronic item outside a store in Caracas / Reuters

As journalists, policymakers, and activists of various stripes and interests focus on the rise of the global middle class, scholars struggle with how exactly to define this category of people worldwide. The method matters, as differences can make one exceedingly optimistic or pessimistic as to today's reality, tomorrow's promise, and of what people, governments, companies, and markets should and should not be doing to encourage this growth.

One way of measuring the middle class is in relative terms, by looking at who is within the middle range of incomes in any given country. Scholars such as Lester Thurow, Nancy Birdsall and William Easterly have done this in various formats. But it is often unclear exactly what their results mean for emerging economies, where the middle of the country is not necessarily one and the same as the middle class. It is also hard to use this approach comparatively, as the "central" income range differs widely from country to country.

Another approach is to use absolute thresholds, which has the advantage of getting at attributes that are more universally acknowledged as middle class. The question here becomes how to define this "fixed band." The most expansive calculation - used by Martin Ravallion at the World Bank -- classifies a middle class person as anyone who makes between $2 and $13 a day in PPP terms. Intended to measure the expansion of the middle in emerging markets, this definition includes those who have just made it across the World Bank $2 poverty line. By this measure, China and India have made incredible strides over the past fifteen years, developing a true middle class. But to those in advanced Western economies many of these people would almost certainly be considered abjectly poor, questioning the comparative value, and universality of this scale.