Berthold was an active member of the Economics Department. He obtained his Ph.D. at the European University Institute in 1996 and joined the department in 2003. He has contributed a great deal since then, having supervised several graduate students and contributing to the development of many others. He was an outstanding teacher and presenter of academic work, and won the college-wide W. P. Carey Outstanding Graduate Teaching Award in 2019. Berthold will be greatly missed.

Berthold's work concentrated on the study of economic development from a macroeconomic perspective, and his work was published in leading journals in the profession. His research consistently blended economic theory with careful measurement and data. He made multiple contributions to our understanding of the ultimate drivers of income and productivity differences across countries, ranging from the role of barriers to entry and trade on Total Factor Productivity, to the examination of what sectors make poorer countries unproductive.

Berthold's more recent contributions to the growing literature on the economic transformation — the reallocation of resources away from agriculture to the manufacturing sector and ultimately to the service sector — have been particularly influential. In several papers, he tackled a host of research questions on the topic, ranging from the nature of preferences consistent with the structural transformation, to the properties of technologies and rates of technical progress behind the structural transformation. His work has become over the years a mandatory reference for work in this area.