The holiday season represents about 20% of total retail industry sales, according to the National Retail Federation. For that reason, Black Friday, considered the busiest shopping day of the year, is a major deal. How the day goes will be the subject of much discussion, debate, and media attention.

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In fact, maybe you’ve already heard about how retailers and those watching the economy are concerned that this holiday season may be the worst since 2009.

Here’s the hitch. Since we don’t get formal data about Thanksgiving weekend sales until weeks later, after the companies and government statisticians have crunched the numbers, we rely on various projections and surveys to figure out how it went. And according to Barry Ritholtz, CIO of Ritholtz Wealth Management, “For the most part … they have nothing whatsoever to do with how retail sales are actually going.”

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So do these projections serve any purpose? Sure. Ritholtz says they play up to this “giant hypefest, this huge consumer orgy,” that never seems to be accurate when we actually get the real numbers.

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Ritholtz says the National Retail Federation is the "prime offender" of this practice . This year, the NRF is projecting holiday sales to rise 3.9% to $602.1 billion. Check out the accompanying video to see what Ritholtz says about how the organization comes up with those numbers.

The results speak for themselves. And they're nothing new. See what Ritholtz points in this recent Bloomberg article:

In 2005, the NRF forecast a 22 percent increase in holiday shopping gains for the Thanksgiving weekend. Full holiday retail sales were up just 1 percent. In 2006, it was a 18.9 percent sales increase, versus less than 5 percent actual gains. In 2007, a 4 percent gain was actually a 0.4 percent drop. NRF forecasts for 2008 were even worse, 2.2 percent sales gain versus a drop of 6 percent.

But nothing compares to the NRF’s 2009 Holiday Consumer Intentions and Actions Survey for holiday shopping -- it forecast a stunning 43 percent fall versus actual sales, which were up about 3 percent.

So if you must prognosticate and don’t have the patience to wait for the official data, Ritholtz recommends looking out for some of the data released by credit card companies. He says far from perfect, but better than other surveys, is the Mastercard Spending Pulse. That’s because it tracks actual spending at the cash register by consumers whipping out their credit cards.