His research fields include macroeconomics, labor economics, and monetary economics. Mueller has published research in journals such as the Journal of the European Economic Association, the American Economic Review, Brookings Papers on Economic Activity, Economics Letters, and the Journal of Public Economics. Awarded the Arnbergska Prize by the Royal Swedish Academy of Science in 2012, Muller holds a PhD in economics, IIES, from Stockholm University and bachelor's and master's degrees in international relations from the Graduate Institute in Geneva.