The middle class is a class of people in the middle of a social hierarchy. Its usage has often been vague whether defined in terms of occupation, income, education or social status. The definition by any author is often chosen for political connotations. Writers on the left favor the lower-status "working class". Modern social theorists—and especially economists—have defined and re-defined the term "middle class" in order to serve their particular social or political ends.
Within capitalism, "middle-class" initially referred to the bourgeoisie; later, with the further differentiation of classes as capitalist societies developed, the term came to be synonymous with the term petite bourgeoisie.
The common measures of what constitutes middle class vary significantly among cultures. On the one hand, the term can be viewed primarily in terms of socioeconomic status. One of the narrowest definitions limits it to those in the middle fifth of the nation's income ladder. A wider characterization includes everyone but the poorest 20% and the wealthiest 20%.[1] Some theories like "Paradox of Interest", use decile groups and wealth distribution data to determine the size and wealth share of the middle class.[2]