Professor Nobuhiro Kiyotaki delivered the 2002 Klein Lecture at the Institute of Social and Economic Research, Osaka University, on April 24, 2002, and it was a big success. The Klein Lecture was established in 1997 in honor of Professor Lawrence R. Klein, who was awarded the Nobel Prize in Economics in 1980. He was, together with Professor Michio Morishima, one of the co-founders of the International Economic Review. Each year, one of the world's most distinguished economists is invited to give a lecture at either the University of Pennsylvania or Osaka University, and the presented paper is subsequently published in the International Economic Review. Professor Fumio Hayashi (University of Tokyo) gave the first Klein Lecture at Osaka University on December 17, 1999, on "Identifying a Liquidity Effect in the Japanese Interbank Market," and it was published in the International Economic Review, vol 42, no. 2 (May 2001).