Coffee at a friend's! We sat trying to make conversation while her three children grappled (扭打) with one another on the floor. Suddenly I remembered that I had brought some glass marbles (玩具子弹) with me—a whole bag full. I spilled them out on the floor, in the hope that the little angels would play with them in peace. Far from it: a heated argument broke out. I didn't understand what was happening until I looked more closely. Among the countless marbles there was just one blue one, and the children fought for it. All the marbles were exactly the same size and shiny and bright. But the blue one had an advantage over the others—it was one of a kind. I had to laugh at how childish children are!

   Rata sunt cara, said the Romans. Rare is valuable. In fact, the scarcity error is as old as mankind. My friend with the three children is a part-time real-estate (房地产) agent. Whenever she has an interested buyer who cannot decide, she calls and says "A doctor from London saw the plot of land yesterday. He liked it a lot. What about you? Are you still interested?"The doctor from London—sometimes it's a professor or a banker—is, of course, not true. The effect is very real, though: it causes prospects to see the opportunity disappearing before their eyes, so they act and close the deal. Why? This is the potential shortage of supply. Objectively, this situation is incomprehensible: either the prospect wants the land for the set price or he does not—regardless of any doctors from London.

   In one study, students were asked to arrange ten posters in order of attractiveness—with the agreement that afterward they could keep one poster as a reward for their participation. Five minutes later, they were told that the poster with the third highest rating was no longer available. Then they were asked to judge all ten once again. The poster that was no longer available was suddenly classified as the most beautiful. In psychology, this phenomenon is called reactance: when we are deprived (剥夺) of an option, we suddenly consider it more attractive. It is also known as the Romeo and Juliet effect: because the love between the tragic Shakespearean teenagers is forbidden, it knows no bounds (难以自己).

   In conclusion: the typical response to scarcity is failure in clear thinking. Assess products and services solely on the basis of their price and benefits. It should be of no importance if an item is disappearing fast, nor if any doctors from London take an interest.