"Imagine I give you a choice: Do you want to go for a weekend to Rome, all expenses paid -- hotel, transportation, food, a continental breakfast, everything -- or a weekend in Paris? Now, weekend in Paris, weekend in Rome -- these are different things. They have different food, different culture, different art. Imagine I added a choice to the set that nobody wanted. Imagine I said, "A weekend in Rome, a weekend in Paris, or having your car stolen?" It's a funny idea, because why would having your car stolen, in this set, influence anything? But what if the option to have your car stolen was not exactly like this? What if it was a trip to Rome, all expenses paid, transportation, breakfast, but it doesn't include coffee in the morning? If you want coffee, you have to pay for it yourself, it's two euros 50.Now in some ways, given that you can have Rome with coffee, why would you possibly want Rome without coffee? It's like having your car stolen. It's an inferior option. But guess what happened? The moment you add Rome without coffee, Rome with coffee becomes more popular, and people choose it. The fact that you have Rome without coffee makes Rome with coffee look superior, and not just to Rome without coffee -- even superior to Paris."