"It's just that the market has grown faster than we have," Burk continued. "While we watch all the external reporting agency numbers diligently, there continues to be a lot of volatility in share numbers month to month. We're watching our own internal data and feel good about the direction those numbers are heading, specifically around [unique users] as an indicator of new people coming to Live Search and liking what they see when they get there."

[Update, 9:42 p.m.: Burk clarified what portion of the market she was referring to in another e-mail: "We are seeing growth in unique users. ... While we are seeing a decline in unique queries internally as well, the decline is not as significant as the Nielsen numbers suggest. We don't disclose the internal data for competitive reasons, but from our comparisons with other reporting agencies, Nielsen numbers are typically the most volatile."

Also, I've added the following table, which illustrates what she's talking about.

Finally, I corrected the spelling of Burk's name.]

In November, according to Nielsen, Live Search queries decreased 16.7 percent, year over year, while total queries increased 6.7 percent.

In October, Live Search was off 19 percent, while the total also decreased by 2 percent.