Your company has a mobile application to help people find the best airline flights. A marketing manager proposed adding a new feature to the application called, "rapid flight check." This new feature would sell a ticket at a deep discount for customers who check the application more frequently. It would almost act the same way as an online ticket raffle system. In this system, ad revenue would increase as people would be encouraged to check their phone more often. Their pilot project showed that even if the customer got a discounted ticket only 1% of the time, engagement still increased. What is this effect called