When Lou Dobbs left his anchor position at CNN under a cloud of controversy last year, he was drawing approximately 630,000 viewers a night. When he debuts early next year on Fox Business Network, it's certain Dobbs won't attract nearly that large of an audience for the last-place cable business channel. But exactly how many viewers do tune into Dobbs will likely be a mystery for the simple reason that Fox Business Network isn't yet officially rated.

That's right, Rupert Murdoch's cable channel appears to draw such a small audience that three years after its launch, and three years after Murdoch pledged to spend $100 million to revolutionize the industry, FBN is still not a full-service Nielsen client. That means FBN execs are not allowed to publicly release the channel's ratings numbers. It's a move that likely saves Murdoch from public embarrassment since the FBN audience for its business shows is assumed to be quite small, somewhere in the low five-figure range, and far behind leader CNBC. (FBN's non-business Imus in the Morning does better in the ratings.)

But I'm sure Dobbs will be quite happy at Fox Business Network.

At the time of the Murdoch channel launch in late 2007, representatives suggested FBN would be fully rated in six or nine months. It's now been three years and still no action.

Why the delay? The official line from FBN execs is that they have concerns about Nielsen ratings and aren't sure the rating firm can properly count (the elusive) Fox Business viewers. Here's what Kevin Magee, FBN's Executive Vice President, told an interviewer earlier this year:

We don't release ratings because we're not a full-service Nielsen subscriber. We need to have a bit more faith in their ability to count our heads.

That's all very interesting. But of course, sister channel Fox News relies on Nielsen numbers all the time and Murdoch execs there constantly cite those TV tallies to trumpet their Fox News successes. But for some reason over at FBN, Nielsen's numbers are no good.

As TV industry analyst Andrew Tyndall once noted, “If the PR people at Fox Business had any numbers to brag about, you can bet they'd be doing it. Their silence speaks volumes.”

The exception was on Election Night, when FBC did do well and outperformed CNBC. Suddenly TV writers were mysteriously all very aware of the fact that Nielsen numbers confirmed that finding. I'll give you one guess what the source of those numbers was. (Hint: They didn't come from CNBC flacks.) So it appears that once a year or so when FBN comes out on top of the business news ratings game, the Nielsen numbers are legit. But for the other 364 days of the year, FBN tells everyone to just ignore those unreliable Nielsen numbers.

And for the record, it's true that Bloomberg TV, another player in the cable business game, is not fully rated and does not disclose its numbers. But it's also true that Bloomberg's TV audience is among the wealthiest and most sought after in all of cable television, which means for them those Nielsen numbers don't really matter all that much.