Monopolistic competition is a market structure characterized by many small businesses that sell differentiated products or services. While firms compete with each other's products, each product is still somewhat unique due to real or perceived differences. This allows firms some monopoly power over their particular product. In the long run, free entry and price competition among existing firms will drive profits back down to zero, but monopolistically competitive firms will still produce at a level below minimum efficient scale, resulting in some excess capacity. Compared to perfect competition, monopolistic competition can lead to deadweight loss from prices above marginal costs and unused resources from excess capacity.