The global economic growth from the 70s quadrupliqued global economic output and created the middle classes in the emerging markets. People in those countries is more educated, connected, richer, etc. than ever.
BUT neither country in ant event, has grown fast enough economically to provide jobs for ever-larger cohorts of young people. The result is political revolution. Besides, societies fail to provide an answer to rising economical expectations for economic and social advancement.
While the poor struggle to survive from day to day, disappointed middle classes are much more liked to engage in political activism to get their way. Families with durable assets like a house or an apartment have a much greater stake in politics since this things are the ones Gov can take away from them.
Middle classes status is well defined by education, occupation, and the ownership of assets, which are far more consequential in predicting political behavior.
People in this category is to grow from 1.8 billion in 2009 to 3.2 billion in 2020, and 4.9 billion in 2030 out of a projected global population of 8.3 billion. The bulk of this growth will occur in Asia: China and India. But everyone will participate in the trend, including Africa (the African development bank estimates 300M people in there now).