As Rush Limbaugh's show enters a second week largely without advertisers -- except, ironically, for government-sponsored public service announcements -- it's worth asking how big a sacrifice it is for brands such as AOL and AllState to stay away from the show.

Limbaugh's show reaches 15 - 20 million people weekly across more than 600 radio stations on which he is syndicated, it is frequently reported.

Or does it?

We asked Arbitron, the radio ratings measurement service, to give us data for Limbaugh. This is what spokesperson Kim Myers said:

"Unfortunately, we don't have show specific data for network programs. The syndicators, Premiere Radio Networks, are the only ones that have the station clearances. Without that, we can't figure out the show ratings data."



"If you want to look at the number of different listeners tuning into Rush's show, you'll want to look at CUME [the cumulative number of people who listen to the show weekly].Again, the only place you can get that information is through Premiere Radio Networks which is based in Los Angeles."

To put that simply, the only reason we "know" that 15 million people listen to Limbaugh is because the company that gets paid for syndicating Limbaugh tells us so. A message asking PRN to explain their methodology was not immediately returned.

A couple of years ago, the Washington Post tried to get to the bottom of the mystery:

"... estimates of Limbaugh's nationwide (and overseas) audience are exercises in guesswork, slippery methodology and suspect data. Limbaugh himself has muddied the water with the claim that he reaches 20 million people a week, although there's no independent support for that figure."



"Premiere Radio Networks, Limbaugh's national syndicator, estimated last year that 3.59 million people were in Limbaugh's audience during an average quarter-hour of his program, based on a review of Arbitron's piecemeal data about hundreds of stations."



"Because people typically tune in and tune out of stations, however, that number doesn't reflect how many individuals cumulatively listened at some point during the week. What's more, Premiere's figure is based on data from the first three months of 2008, a virtual lifetime ago in the fast-moving radio business."

Basically, this "15-20 million" number has been floating around the media unaudited for four years. Even if you assume, generously, that the CUME number holds true, here is how that would break down in real life, according to Media Matters:

"...common industry shorthand to determine the actual size of a radio audience at any given moment is to cut the cume figure down by a factor of 10, which would mean Limbaugh's 20 million becomes 2 million. Or, if you take the more modest cume number of 14 million, which some inside the industry have used to judge the talker's audience, Limbaugh's rating becomes 1.4 million, which is roughly the same size audience that Rachel Maddow and Keith Olbermann get each night on cable TV."

So there is it: Absent better data, only 1.4 million people listen to Limbaugh at any one time.