Trading stamps were small paper coupons, given to customers by merchants, that had a minimal cash value. Customers could save these coupons and exchange them with the trading stamp company for premiums. The use of these coupons grew with the proliferation of chain gas stations and supermarkets in the early 20th century. After World War II, the use of trading stamps expanded even further when supermarkets began to use them as a customer incentive. In the 1970s, the energy crisis caused gas stations to stop offering the stamps and although there was a slight resurgence in the 1980s, the practice died out soon after when supermarkets and other businesses began using rewards cards and other programs as incentives. Eagle Stamps, the last trading stamp company in the United States, closed in 2008.