By TIM ARANGO


In one of the many smoky scenes in“Mad Men,”the critically loved television show about the advertising world in the era of martinis and misogyny in the 1960s, a founder of the fictional advertising firm Rogers & Sterling describes marketing glory.

“I’ll tell you what brilliance in advertising is,”says the actor John Slattery in the character of Roger Sterling.“99 cents.”

It may be just the insight retailers are looking for as they struggle to stimulate consumer spending in this trying time: If you can’t sell something for 99 cents, you should at least tack on .99 to the price.

Steven P.Jobs, the chief executive of Apple Computer, tried the 99-cent approach and arguably saved the music industry from oblivion.

In picking that one standard price for each song for sale on iTunes, Mr.Jobs built a commercially viable digital delivery business for music. Before the start of iTunes in 2003, it was a questionable proposition that people would ever pay for music online when they could steal it from any number of peerto- peer networks.

Dave Gold also tried it. In the 1960s, he and his wife owned a liquor store in Southern California where they sold wine at various prices: 79 cents, 89 cents, 99 cents and $1.49.

“We always noticed that the 99 cents sold much better,”he recalled in an interview.

They priced all their wine at 99 cents, and overall sales improved.

“The 79 cents sold better at 99, the 89 cents sold better at 99, and of course the $1.49 sold better at 99,”he said.

Mr.Gold and his wife eventually took the concept to the extreme and in 1982 started a chain of 99 Cents Only stores. They took it public in 1996, and today the company has 282 stores and is worth more than half a billion dollars. In the last quarter, sales were up 8 percent; profits, 31 percent.

Mr.Gold wasn’t the first to strike on 99 cents as a lucrative marketing gimmick, but he may have done the most with it. No one quite knows who came up with the concept. Regardless, the marketplace power of.99 seems undeniable. But why?

Academics have offered a variety of psychological explanations. One study, by Robert M.Schindler, a professor of marketing at the Rutgers School of Business in New Jersey, found that consumers“perceive a 9-ending price as a round-number price with a small amount given back.”Researchers have also found that prices ending in .99 communicate“low price”to consumers.

At the University of Chicago, for instance, researchers found that when the price of margarine dropped from 89 cents to 71 cents at a local grocery chain, sales improved 65 percent, but that when the price fell to 69 cents, sales rose 222 percent, according to Kenneth Wisniewski, an author of the study.

And Professor Schindler, in a study at a women’s clothing retailer, found that the one-penny difference between prices ending in .99 and .00 had“a considerable effect on sales,”according to his study, with items whose prices ended at.99 outselling those ending at.00.

So when retailers price their wares with a figure ending in 9, the reason is simple, Professor Schindler said.

“It’s to make the price seem like it’s less.”