It's no secret that Americans eat a lot of pizza. In fact, around 13 percent of the country is eating a slice or two on any given day, according to a new report from the USDA:

It all adds up to a lot of calories: On an average day, the report notes, pizza provides 6 percent of the total caloric intake for American children and 4 percent for American adults.

But there's also a subtle policy angle here. Pizza is popular because it's delicious. But the roaring success of pizza isn't entirely a free-market story. "In recent years, [the USDA] has spent many millions of dollars to increase pizza consumption among U.S. children and adults," explains Parke Wilde of Tufts University, who runs the excellent U.S. Food Policy blog.

How the U.S. government promotes pizza

Here's what he's referring to. The USDA runs a "dairy checkoff program," which levies a small assessment on milk (15 cents for every hundredweight of milk sold or used in dairy products) and raised some $202 million in 2011. The agency then uses that money to promote products like milk and cheese. And, as it turns out, pizza.

The USDA claims its checkoff program has been well worth it: For every $1 that the agency spends on increasing cheese demand, it estimates that farmers get $4.43 in additional revenue. But the results have been mixed. Milk consumption has declined in recent decades, while cheese consumption has soared:*

The program also helps pizza makers, who use one-quarter of the nation's cheese. A 2010 USDA report details how Dairy Management, Inc. (DMI), a corporation funded by these checkoff fees, spent $35 million in a partnership with Domino's to boost pizza sales:

Domino’s has partnered with DMI since early 2009 using dairy farmer dollars to develop and to promote Domino’s pizza offerings. In February 2009, Domino’s launched the American Legends line of pizza. This line featured regional specialties such as the Honolulu Hawaiian, the Cali Chicken Bacon Ranch, the Pacific Veggie, the Buffalo Chicken, the Philly Cheese Steak, and the Memphis BBQ Chicken, and was advertised as having 40 percent more cheese than Domino’s typical pizzas. Cheese also was used on the crust. Later, Domino’s expanded the line from six to eight different pizzas, adding the Fiery Hawaiian and the Wisconsin 6 Cheese. According to Patrick Doyle, President and CEO of Domino’s Pizza, “DMI support has allowed us to focus some advertising dollars on areas we would not have considered otherwise. The Wisconsin 6 Cheese pizza has twice the cheese of a regular pizza, but we had neither developed nor advertised such a product. DMI helped fund the research and media to launch this product."

According to the report, the dairy checkoff program also worked with McDonald's to launch McCafe specialty coffees and three new burgers with two slices of cheese on them. It also helped Yoplait develop new yogurt chip technology. The program was renewed in the most recent farm bill.

So what's the problem? Critics of this program often note that efforts to promote fruits and vegetables haven't received nearly the same level of support as dairy and meat products (a few fruits do have their own checkoff programs, including blueberries and watermelons, but not many). That imbalance doesn't explain the popularity of pizza, obviously, but it's one extra unseen force at work here.

Further reading:

-- Back in January, Siddhartha Mahanta took a longer look at the checkoff program for beef in the Washington Monthly.

-- Somewhat more randomly, here's a report on how the dairy industry is hoping that chocolate milk can halt declining milk consumption.