Today is National Fast Food Day, so naturally we felt it was a perfect time to do the numbers on the U.S. fast food industry's biggest players. The chart above shows the change in sales in the last five years, using data from an IBISWorld report published in May. McDonald's holds 15.8 percent of the market share of the fast food industry, followed by Yum! Brands Inc., which holds 8.9 percent and, finally, Subway with 5 percent. Yum! Brands Inc. includes three major fast food chains: Kentucky Fried Chicken, Taco Bell and Pizza Hut.