A new Middle Market Power Index from American Express and Dun & Bradstreet ranks Iowa 24th among the states in the share of firms that are in the middle market. Iowa has an estimated 1,596 middle market firms, which are defined as businesses generating between $10 million and $1 billion in revenues. Nationally, there are more than 136,000 middle market firms, which employ an average of 368 workers and generate $45.1 million per firm per year. The middle market makes up less than 1 percent of U.S. businesses, but contribute 21 percent of U.S. business revenues and employ 28 percent of workers in private businesses.