These are the books Prince is carrying with him to Nigeria. The rest are being shipped. It took us most of the morning to go through the books. I went through each book and asked "Ship or carry?" and he answered his first 20 books "carry." After that, he had to trade me a book he had already chosen for another book. It took some doing, but we're pretty happy and think his final choices reflect his true interests.
By comparison, when I realized we had another stack of hardback books he had to go through and I had him make pairwise choices, every choice was to get rid of his last choice and take the new book. That was ridiculous. He ended up with a book he hasn't asked for in a long time. So instead we presented him that book and 4 others we knew he liked and he chose one of the others.
As an economist, this was interesting. How to reveal true preferences and a test of toddler rationality. His preferences expressed the first way were quite rational. The second way, not so much: he prefers The Marvelous Toy to the Squirrel Tale, but then he prefers the Squirrel Tale to The Marvelous Toy. Not rational. Or at least, it appears to be not rational. Really, it means the mechanism I used to elicit his preferences failed.
Now to figure out how to get him to choose among his toys!