So, what class are you?

How does one define the vague term 'middle class'?

In India, a scooter company aims ads at a schoolteacher who earns $2,500 a year and lives in a tiny brick house with no running water. Why? Because that teacher, according to marketers, is middle class. In the United States, meanwhile, a family that earns $200,000 a year and has a 2,000-square-foot home, two cars, three computers and an Xbox game console so the kids don't have to play outside barely blinks before labeling itself middle class.

And yet, experts say, neither is incorrect:

• The Indian teacher, despite his relative poverty, earns an extra sliver of income that will allow him to buy something he doesn't absolutely need. He has escaped poverty.
• The American family, although extremely wealthy by world standards, lives with some degree of financial stress. Both parents work hard but worry about retirement, education and health care costs, and are acutely aware of the fact that they share a country with some who have far more. They feel middle class.

"Everybody sort of defines themselves as middle class" in America, says Steven R. Pressman, a professor of economics and finance at Monmouth University in West Long Branch, N.J. "Self-perception is a funny thing."