The success as well as the recent misfortunes of the post-war Japanese economy has been one of the most debated points in economics. Many explanations focus on cultural and institutional factors, and in particular the role of "Informality" in networks organizing business activity and government policy. This book provides the first quantitative and qualitative assessment of Informality in the formation of Japanese monetary policy. The author spent two years at the Institute for Monetary and Economic Studies at the Bank of Japan and the Japanese Ministry of Finance and offers a unique "insider-outsider" perspective.