Responded Obama spokesman Jay Carney: The middle class is the "principal preoccupation" of Obama's presidency.
The meaning of "middle class" has grown even harder to parse following a populist Occupy movement that for months protested high unemployment and income inequality with a rallying cry of "We are the 99 percent."
Formal definitions vary, but few academics would say it covers more than 60 percent of Americans.
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.