Where is Africa's Catalytic Class?

Responding to a report that 1 in 3 Africans are in the middle class Andy Sumner and Nancy Birdsall write in the Guardian:

...is someone living on just over $2 a day "middle class"? Two dollars is the average poverty line for developing countries, meaning you're poor or middle class – but what about in between?

On definitions:

Courtesy of SACCA

There are various definitions of middle class in what is a burgeoning area of interest for poverty reduction research – stimulated perhaps by ideas about the middle classes as change-makers or catalysts.

Or should we be looking at those with a 'A Culture of Production'

Courtesy of travelpod

What about the idea of a catalytic class? This is the idea: the catalytic class is a group, whose expansion triggers internally driven, self-sustaining, political and economic change, a group whose exertion of pressure for better governance and economic reform leads to change when the class hits a certain size (in population or economic or tax revenue size). The interests of this class coincide with the interests of the poor.

More here