Pierre-Andr� Chiappori is Professor of Economics at Columbia University.Bernd and Hilla Becher have collaborated since 1959. Founders of the internationally acclaimed Becher class at the Dusseldorf Art Academy, they have received numerous awards, including the Golden Lion at the 1990 Venice Biennale and the 2002 Erasmus Award. Bernd Becher retired as Professor at the D�sseldorf Academy of Art in 1999.