When it comes to earnings, the Census Bureau divides household income into quintiles, or groups of 20 percent. Some economists narrowly define the middle class as those in the middle 20 percent of the distribution, earning between $38,000 and $61,000. Others define it more broadly to include the middle 60 percent of the income distribution, between $20,000 and $100,000.
Defining who is poor, by contrast, is officially more absolute. The federal poverty line is based on the minimum income needed to have what the government considers a basic standard of living. Two times the poverty line is often a cutoff for "low-income" families who may be eligible for government aid. The poverty line currently is $22,314 for a family of four, meaning that a family making $44,000 could be both "low income" and "middle class."
Yet another way to gauge class is what income tax bracket you're in. The IRS has six of them. This year, the bottom bracket sets a tax rate of 10 percent for taxable income up to $17,400 for couples. The top bracket is 35 percent, applied to taxable income above $388,350. The middle class is commonly seen as falling in the 15 and 25 percent brackets, or couples whose taxable income is between $17,400 and $142,700. But some define it all the way up to the second-highest bracket, which is 33 percent and includes taxable income up to $388,350.
Sociologists take a broader view and focus not on income, but occupation: an "upper middle class" of white-collar specialists (lawyers, engineers, professors, economists and architects); and a "middle class" of lower-level white-collar workers (teachers, nurses, insurance sales and real estate agents). Together, these groups make up about 45 percent of households and sit near the upper end of the income distribution, just behind the top 1 percent.
The meanings shift more dramatically when measured by self-identification and quality of life.
Few Americans label themselves as upper class or lower class, which are seen as either pretentious or demeaning. Roughly 95 percent of adults say they are middle class (50 percent), upper middle class (13 percent) or working class (32 percent), according to a Washington Post-ABC News poll conducted in May. Just 2 percent describe themselves as "better off" than upper middle class.