DES MOINES, Iowa - If you live in the Midwest, chances are you've got a couple of frozen pizzas at home. And probably a few more on your shopping list. You might even be chewing a mouthful of one now.

The odds are good because the typical Midwesterner ate frozen pizza 22 times last year - a rate nearly double the national average of about 13 times a year, according to a study by a New York market research firm.

What is with the Midwest and frozen pizza?

"It's fast and convenient," Holly Gilliland, a mother of four from West Des Moines, said recently while browsing frozen pizzas at Hy-Vee in West Des Moines. "It's less expensive than ordering out."

Maybe. But convenience only explains why frozen pizza has evolved into a $2.4 billion national industry, not what makes Midwesterners love it so, said Andrew Smith, the editor of "The Oxford Companion to American Food and Drink."

How do you explain that the typical Hy-Vee grocer - of which there are 220 in the Midwest - stocks more than 1,000 varieties of frozen pizza in more than 60 feet of freezer space, and always features a frozen pizza in its weekly sales?

"I have no idea why, but I think it's the same pizza sold over the world," said Mike Kueny, director of a Des Moines Hy-Vee.

Perhaps it's the food's local roots. After all, the Midwest did popularize the stuff.

Credit goes to Rose Totino, who in 1951 opened a pizzeria in Minneapolis. The growing demand for frozen foods overall persuaded her that pizza needed a slice of the business, and in 1962 she launched the first popular national frozen pizza brand.

But pizza itself wasn't born in the Midwest, which Barb Stuckey thinks might explain the frozen pizza fascination. Stuckey is vice president of marketing for Foster City, Calif.-based Mattson, a food developer that has played a big role in the frozen pizza industry.

New York was home to the first licensed American pizzeria, and California's innovative chefs are credited with pushing pizza in new and exciting directions.

"Because of that, pizza in the restaurant segment is probably stronger on the coasts, and so people need to scratch that itch less frequently with frozen pizza," she said.