Matthew E. Kahn is the Bloomberg Distinguished Professor of Economics and Business at Johns Hopkins University and the Director of JHU's 21st Century Cities Initiative . He is a research associate at the National Bureau of Economic Research and a research fellow at IZA. He has taught at Columbia, the Fletcher School at Tufts University, UCLA and USC. He has served as a Visiting Professor at Harvard and Stanford and as the Low Tuck Kwong Distinguished Visiting Professor at the National University of Singapore. He is a graduate of Hamilton College and the London School of Economics. He holds a Ph.D. in Economics from the University of Chicago. He is the author of Green Cities: Urban Growth and the Environment (Brookings Institution Press 2006) and the co-author (joint with Dora L. Costa) of Heroes and Cowards: The Social Face of War (Princeton University Press 2009). He is also the author of Climatopolis (Basic Books 2010) and Blue Skies over Beijing: Economic Growth and the Environment in China (joint with Siqi Zheng published by Princeton Press in 2016). He has also published three other Amazon Kindle books on urban economics and microeconomics. His research focuses on urban and environmental economics.