The middle class now makes up more than half the world population for the first time in history thanks to the rapid growth of developing countries such as Brazil, China and India, the Economist reports. The middle class only accounted for one-third of the world population in 1990 but mushroomed to 57 percent in 2006.

However, definitions vary. Indian economist Surjit Bhalla classifies the middle class as those earning $10-100 a day, while according to Diana Farrell, now a member of the U.S. National Economic Council, it is people who have one-third of their income left after paying for basic food and shelter.

Using Bhalla's definition, the demographic changes in the global bourgeoisie were led by developing countries and Asia. There the middle class, which accounted for one-third of the population in the 1990s, makes up 49 percent as of 2005. In China, the percentage of people who earn at least US$3,900 per year was 5 percent in the 1980s but over 70 percent in 2008. But while the middle class burgeoned in Asia, in the West it has lost its footing after peaking with 70 percent in 1950, standing at a paltry 20 percent as of 2006.

Abhijit Banerjee and Esther Duflo, of the Poverty Action Laboratory at the Massachusetts Institute of Technology, told the weekly the middle class will be "the dominant force in establishing or consolidating democracy," and "the backbone of the market economy."