This will involve some daring, with the aircraft spending all day climbing as its batteries are recharged and then descending slowly under power throughout the night to conserve energy.

ECONOMIST: Solar-powered manned flight

But a frequently asked question these days is: Are we exceeding the optimal point of inequality and descending into an era of a vanishing middle class and, with it, the spending power and inclination with which it fuels an economy?

FORBES: Is 'Conscious Capitalism' an Antidote to Income Inequality?