This year, at least a dozen major retailers opened on Thanksgiving. | AP Photo

By ASSOCIATED PRESS | 11/30/13 6:13 PM EST

Thanksgiving Day is no longer all about turkey: It’s eating away at Black Friday shopping.

U.S. shoppers spent $9.74 billion at stores on Black Friday, the day after Thanksgiving. That’s a drop of 13.2 percent compared with the same day last year, according to preliminary data released on Saturday by research firm ShopperTrak.

The decline appears to be because more Americans were shopping on the holiday itself: Combined spending on Thanksgiving and Black Friday, which had previously been considered the official start to the holiday buying season until this year, rose 2.3 percent to $12.3 billion.

The data shows that Thanksgiving, which along with Christmas had been one of only two days that most stores are closed each year, is becoming an increasingly important shopping day for major retailers.

Black Friday used to be the time when retailers would open early and offer deep discounts to draw shoppers into stores. But a few retailers started opening on the holiday in the past couple of years. And this year, at least a dozen did so, with a few opening earlier in the holiday than they did last year.

The National Retail Federation predicted that 33 million, or almost a quarter, of the 140 million people who planned to shop during the four-day holiday weekend that ends on Sunday, would do so on Thanksgiving. And analysts had questioned whether the holiday openings would steal sales away from Black Friday or result in people spending more overall.

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