New York ? The average American planned to spend $835 on holiday purchases this year, according to financial education organization Myvesta’s annual survey, and this is the time of year we ask ourselves, “Why?”

A lot of cultural forces are at work — from cartoons whose furry characters are coveted toys to celebrities touting the latest fashions to your office’s Secret Santa traditions — that urge you to get out there and spend, spend, spend. Factor in amenities like baby-sitting at some major department stores or the convenience of shopping online, and add the delayed consequences that credit card purchases offer, and it’s an intoxicating mix that’s difficult to resist.

“For a lot of people I almost consider it a sport,” says Canadian journalist Pamela Klaffke, author of “Spree: A Cultural History of Shopping” (Arsenal Pulp Press).

The first mall was the Stoa of Attalos in Athens, Greece, in 150 B.C., Klaffke says, but shopping as a leisure activity is a relatively recent phenomenon. In terms of clothing, most was custom-made until the second half of the 19th century, when ready-to-wear clothes began to be sold.

“Before that, it wouldn’t have crossed anybody’s mind to shop because there was nothing to buy,” Klaffke says.

Stores began to serve as social salons for women in the late 19th century, and this culminated in the mall culture that emerged in mid-20th century.

But the days of the mall as the center of the teen universe — shown in 1980s and 1990s movies such as “Fast Times at Ridgemont High,” “Valley Girl,” “Mallrats” and “Clueless” — soon will be over, Klaffke says.

“Nowadays the mall doesn’t have the same significance,” she says, citing the rise of “sad malls,” whose main tenant leaves, causing the rest of the shopping center to die a slow death. “These kids didn’t grow up thinking the mall was the best thing ever.”

Instead, teenagers — who are seen as a group with increasing buying power — prefer limited edition shoes and clothes. With magazines like Seventeen, Teen People, Cosmo Girl and Teen Vogue catering to them, teenage consumers have more clout than ever in determining what retailers sell.

“It’s a reaction to the ‘Gap-ization’ of fashion, with khakis and jeans so prevalent. Younger people are rebelling against that, they want something special,” Klaffke says. “They have a ridiculous amount of disposable income.”

In “Spree,” Klaffke veers easily from the business of retailing to pop culture analysis, including her list of “five shopping scenes not to be missed”: Audrey Hepburn’s romp through Tiffany & Co. in “Breakfast at Tiffany’s”; Arnold Schwarzenegger’s cry of “Let’s go shopping!” as he drives a tank into the front of a store in “Commando”; Julia Roberts’ revenge on snooty Rodeo Drive saleswomen in “Pretty Woman”; Marilyn Monroe’s and Jane Russell’s shopping spree in “Gentleman Prefer Blondes”; and the French musical paean to commerce, “Window Shopping.”

Klaffke also answers a question that insomniacs and other late-night TV watchers have asked themselves for years: Just who are the people who buy things from infomercials? Turns out the average shopper is a married woman between 45 and 55 who has a household income of $56,000 or more and is most likely to buy exercise- or health-related products, according to a 2001 survey conducted by The AfterMarket Co. and Response magazine.

“No matter how they’re shopping, there are people who love it. Then there’s the people who hate to shop, and only do it when they have to,” Klaffke says. “Watch the shoppers’ faces, and you know who’s who.”

But once a bargain is found, Klaffke believes, anyone can be hooked. Witness the person who finds a digital video camera on eBay for $30 or a wedding dress for $200 at a sample sale.

Like a deer head proudly hung in the living room, these hunters proudly trumpet their finds to everyone they know, and thus the shopping culture is spread, Klaffke says.

“It makes you think, if a shopper buys something and doesn’t tell someone, does it really exist?”