Takeaways
The shorter the distance to the goal, the more motivated people are to reach it. People are even more motivated when the end is in sight.
You can get this extra motivation even with the illusion of progress, as in the coffee card B example in the section. There really isn't any progress (you still have to buy 10 coffees), but it seems like there has been some progress so it has the same effect.
People enjoy being part of a reward program. When compared to customers who are not part of the program, Kivetz found that the customers with reward cards smiled more, chatted longer with Cafe employees, said thank you more often, and left a tip more often.
Motivation and purchases plummet right after the goal is reached. This is called a post reward resetting phenomenon. If you have a second reward level people won't initially be very motivated to reach that second reward.
You're most at risk of losing your customer right after a reward is reached.
Book Citation Reference: “Chapter 6 / Section 50.” 100 Things Every Designer Needs to Know about People, by Susan Weinschenk, New Riders, 2011, pp. 116–117.