Costco is a membership warehouse retailer with the bulk of its locations in the U.S. Consumers must purchase a membership to gain the privilege to shop at one of its brick-and-mortar stores (they have employees who check for membership before entry). Over the decades, Costco has gained a reputation among consumers for offering excellent value. That incredible value can partly explain why Costco has sustained an operating profit margin of between 2.8% and 3.4% in the last decade, despite nearly doubling revenue from $99 billion to $196 billion in that time.