CNBC's ratings are down almost 30 percent year-over-year and almost 50 percent on some shows. Theories abound. Perhaps they've taken a PR hit by riding 2007's bull market headfirst into the blazing inferno of 2008. Perhaps America's protector laureate of populist range Rick Santelli actually makes viewers lurch for the volume control button. Or perhaps Jon Stewart's celebrated undressing of manic stock maven Jim Cramer left a bad taste in people's mouth. Whatever.

I think Barry Ritholtz hits this right on the nose. It's best to think of CNBC as more like the Weather Channel and less like NBC. Hurricanes, both Floridian and financial, bring viewers in torrents. We don't watch market news for character development. News volatility trumps programming.

Here's Ritholtz:

In my opinion, these ratings are more or less meaningless. They are not proof of bias or bad programming choices or other assertions. CNBC is a media venue that has surprisingly little control over its own fate. While network executives can occasionally make things better or worse via programming and staffing choices, the tidal wave of forces that ultimately determine the bulk of viewers is in reality far beyond their control.

I think that's mostly right. To be sure, Americans make discriminating choices about how they want their news delivered. Fox Business still lags behind CNBC, ratings differ among the opinionated evening news shouters, and so on.

But CNBC is largely a victim of its source material. Viewership spiked after Bear Sterns' meltdown because everybody was running around like chickens with their heads cut off and CNBC was the business channel. Today, as we emerge slowly from a recession, market news is still important, but we're not as worried about the banks dragging the economy down like an anchor tied to a ballerina's ankle. For heaven's sake, even AIG is turning a profit now! Winter of our discontent made glorious summer! Only, not for CNBC (or these people.)

Ritholtz spots this graph, from The Last Psychiatrist, which shows correlation between CNBC's ratings and market volatility. This isn't proof of his hypothesis (correlation does not equal causation, etc), but it suggests that something -- whether trading volume, or jumpy markets, or incendiary Wall Street news -- is tethering CNBC ratings and market volatility, which should lend a quantum of solace to the network's TV editors.