What Lies Beneath Today's consumers no longer fit into yesterday's molds. Here's how to get a grip on the new demographics--and get inside your customers' heads.

Editor's note: For a short history of demographics, click here.

Age, income, sex and educational level. For decades, companies large and small have depended on these demographic categories to shape their marketing campaigns and make sense of their potential customers.

It might be time to rethink this strategy. Demographics--the quantifiable social and economic characteristics of a population--aren't as powerful as they used to be. "The value of demographics has begun to wear out a little bit. They're increasingly becoming less important," says J. Walker Smith, author of Coming to Concurrence: Addressable Attitudes and the New Model for Marketing Productivityand president of Yankelovich Partners, a market research and consulting firm in Chapel Hill, North Carolina.