On Jan. 14, violinist Hilary Hahn scored a rare gig for a classical performer: She appeared on "The Tonight Show." And not just any "Tonight Show," but the "Tonight Show" during the final days of Conan O'Brien. Everybody was watching. So it came as no surprise that Hahn's new album, "Bach: Violin and Voice," debuted that week at No. 1 on the Billboard classical charts.

No. 1 on the charts: It doesn't get any better than that. Or does it?

The dirty secret of the Billboard classical charts is that album sales figures are so low, the charts are almost meaningless. Sales of 200 or 300 units are enough to land an album in the top 10. Hahn's No. 1 recording, after the sales spike resulting from her appearance on Conan, bolstered by blogs and press, sold 1,000 copies.

It's not exactly news that album sales in all genres have been declining for years. Nor is it news that classical recordings are not top sellers.

"The classical charts have always been looked at as in the 3-percenter club," says Alex Miller, general manager of Sony Masterworks. "Three percent of total music sales are in classical music."

The idea that the classical recording industry is on the rocks, a suggestion raised from time to time in part because of strikingly low sales figures, is generally countered by the assertion that there are more classical recordings available than ever before. And that might be the reason so few of them are selling well.

SoundScan, the company that provides sales data to Billboard, says it cannot officially release exact sales figures to journalists. Instead, all numbers are rounded to the nearest 1,000, so sales of 501 copies are reported as 1,000, and anything less than 500 is "under 1,000." On last week's traditional classical chart, only the top two recordings managed to sell "1,000" copies. Every other recording (including, in its second week, Hahn's) sold "under 1,000." The official total sales of the top 25 titles amounted to 5,000 copies, an average of 200 units a recording (sorry, "under 1,000"). And yes, that includes downloads.

A leaked copy of the SoundScan figures for a single week from the fall tells an equally sad tale. In early October, pianist Murray Perahia's much-praised album of Bach partitas was in its sixth week on the list, holding strong at No. 10. It sold 189 copies. No. 25, the debut of the young violinist Caroline Goulding, in its third week, sold 75 copies.

Is there any point to charting such low numbers? Billboard has wondered the same thing. The magazine has two charts, Classical Traditional and Classical Crossover, and combines them on Billboard.com. "We have actually considered decreasing the length of the two separate charts," says Silvio Pietroluongo, charts director of Billboard. Having 25 positions, he says, "may be a bit much."

Weekly charts are not the best way to measure classical performance, industry insiders say.

"We do view our projects initially on a three-year basis," says Sony Masterwork's Miller, adding that the Billboard charts show only U.S. sales. "Murray Perahia," he says, "is an artist that we take a worldwide perspective on. A few hundred units in any given week of Murray Perahia in the U.S. is part of the thousands and thousands that we may sell in Germany or France."

The classical music field is caught in a perpetual bind when it comes to mass-culture benchmarks. On one hand, it wants to aim higher, presenting great art for perpetuity. "Our goal is to build artists," Sony's Miller says. On the other hand, it searches for signs that it matters in the larger culture, in which it is increasingly marginalized - signs such as winning Grammys, and which, like the Billboard charts, are of questionable significance.

If classical music can't make money, it can't stay alive. And it's notable that recordings appear to do worse than concert ticket sales. If everyone who attended the National Symphony Orchestra on a given night bought a copy of the same album, that album would leap to the top of the classical charts every week.

Are the low sales figures a sign of the field's decline or that the charts are outdated? Miller says the charts are for those within the field.

"You need it for historical context," he says: to measure how an artist is doing relative to his or her past chart performance.

"There is a relevance there," he says. "It has to do with retailers, to try to convince retailers" to give the recordings more prominence. "It helps to build the story." The story that's told to consumers to persuade them to buy a recording - and watch it shoot up the charts. In classical music, every single album sale does make a difference.