Forey, Inc. competes against many other firms in a highly competitive industry. Over the last decade, several firms have entered this industry and, as a consequence, Forey is earning a return on investment that roughly equals the interest rate. Furthermore, the four-firm concentration ratio and the Herfindahl-Hirschman index are both quite small, but Rothchild index is significantly greater than zero. Based on this information, which market structure best characterizes the industry in which Forey competes?