Let us start by thinking how we set prices. Suppose we want to buy an airline ticket online. What do we do? Most of us would start by using an online search engine to find prices. But do we buy the airline ticket right away? Many of us would not. We would go back the next day and search for the same ticket again. If the ticket price has gone up, we would be a little more eager to buy. We might be willing to wait an additional day, but if prices go up again on the second day, we would be much more likely to buy immediately. In contrast, if the ticket price has gone down, we would be much more willing to wait. If the ticket goes down in price yet again on the second day, we will be willing to wait even longer.