Increasingly in the United States, advertisements and sales pitches are being aimed at young people. That is because analysts estimate the nation's 9-to-19-year-olds either spend or influence the spending of about $300 billion annually.

First of all, consider the size of this market. The baby boomers the 78 million children born in the U.S. population explosion after World War II have reproduced.

The result, is a large and growing population of young people that marketers are referring to as the "echo boomers."

Next, says Rob Callendar, spokesman for Teenage Research unlimited, a national marketing firm that conducts teen surveys, consider the spending power of these young people.

"Parents are busy. You have got a lot of double income homes where both parents work so they farm out some of the errands to teens. So even things that would not be naturally predisposed to the trendy teen market, like breakfast cereal, teens have a big voice in what actually ends up coming home," he says.

In addition to family purchases, Mr. Callendar says, most U.S. children get allowances from their parents, and most teenagers earn their own spending money. Surveys indicate the average teenager earns $87 a week and spends $81.

"When teens do get money, it is discretionary income for the most part. You and I might have to make a house payment. Kids are all buying the fun stuff, like clothes, so retailers really enjoy the fact that even if the economy slows down a little bit, they are still willing to spend it on things that adults think they can do without," Mr. Callendar says.

Which is why, at a time when retail sales are slowing, stores aimed at young people are increasing 17 percent annually. And researchers are intently studying the youth market. Penn State marketing professor Marvin Goldberg just did a national survey on materialism among children aged nine to 14, trying to analyze the importance of money in their lives. The answers varied.

"There is a small tendency for lower income kids to be slightly more materialistic. More materialistic parents have more materialistic children. Girls tend to be a little less materialistic than boys. Girls tend to be more socially oriented, a little more altruistic," he says.

But, Mr. Goldberg also found that the average 10-year-old American child whether materialistic or non materialistic makes five trips a week to a store.