often not known at the time of purchase. Some consumers may object that it is impossible for them to boycott yield management when buying some goods, such as airline tickets. Yield Management also includes many noncontroversial and more prevalent practices, such as varying prices over time to reflect demand. This level of yield management makes up the majority of yield management in the airline industry. For example, airlines may price a ticket on the Sunday after Thanksgiving at a higher fare than the Sunday a week later. Alternatively, they may make tickets more expensive when bought at the last minute than when bought six months in advance. The goal of this level of yield management is essentially trying to force demand to equal or exceed supply. When yield management was introduced in the early 1990s, primarily in the airline industry, many suggested that despite the obvious immediate increase in revenues, it might harm customer satisfaction and loyalty, interfere with relationship marketing, and drive customers from firms that used yield management to firms that do not. Frequent flier programs were developed as a response to regain customer loyalty and reward frequent and high yield passengers. Today, yield management is nearly universal in many industries, including airlines. Despite optimizing revenue in theory, introduction of yield management does not always achieve this in practice because of corporate image problems. In 2002, Deutsche Bahn, the German national railway company, experimented with yield management for frequent loyalty card passengers. The fixed pricing model that had existed for decades was replaced with a more demand-responsive pricing model, but this reform proved highly unpopular with passengers, leading to widespread protests and a decline in passenger numbers. Experimental studies of yield management decisions Recently, people working in the area of behavioral operations research have begun to study the yield management decisions of actual human decision makers. One question that this research addresses is how much might revenues increase if managers relied on yield management systems rather than their own judgment when making pricing decisions. Using methods from experimental economics, this work has revealed that yield management systems are likely to increase revenues significantly. Further, this research reveals that "errors" in yield management decisions tend to be quite systematic. For instance, Bearden, Murphy, and Rappaport showed that with respect to expected revenue maximizing policies, people tend to price too high when they have high levels of inventory and too