Short answers, pulled from the story.
The phrase middle class appeared for the first time in James Bradshaw's 1745 pamphlet titled Scheme to prevent running Irish Wools to France. This text described a group of people existing between the nobility and the peasantry in late-feudalist society.
Barbara Ehrenreich and John Ehrenreich defined the professional-managerial class in the United States in 1977. Their definition describes salaried mental workers who do not own means of production but reproduce capitalist culture and relations.
By 2013 some 420 million people or 31% of Chinese population qualified as middle class according to Center for Strategic and International Studies. The number grew from 15% to 62% of the population between 1990 and 2005 during that stage of development.
A 2014 study by Standard Bank economist Simon Freemantle found total of 15.3 million households in 11 surveyed nations of Africa are middle class. These nations include Angola, Ethiopia, Ghana, Kenya, Mozambique, Nigeria, South Sudan, Sudan, Tanzania, Uganda, and Zambia.
In 2010 a working paper by OECD asserted that 1.8 billion people were now members of global middle class. This figure represents a significant portion of the world's population at that time.