Finding the appropriate retailer to fill your space is equal parts art and science. But if it's a pizza joint you are looking for things become more clear. The pizza belt theory originated in the summer of 2013 and detailed "the area of the United States where the chance of obtaining an adequate-to-good slice of pizza from a randomly chosen pizzeria is greater than 50 percent." So taking this a step further, Retailsphere located the best expanding pizzerias within the Pizza Belt.