Jan Sonntag

Welcome to my website! I am a PhD candidate at Sciences Po's Department of Economics. I am interested in applied microeconomics, specifically behavioral economics and production networks. My supervisor is Emeric Henry.

More about my research


Most of my papers are still work in progress - please feel free to reach out to discuss a project or obtain early drafts.

Vertical Integration and Foreclosure: Evidence from Production Network Data

With Johannes Boehm

Work in Progress
This paper studies the prevalence of vertical market foreclosure using a novel dataset on U.S. and international buyer-seller relationships, and across a large range of industries. We find that relationships are more likely to break when suppliers vertically integrate with one of the buyers' competitors than when they vertically integrate with an unrelated firm. This relationship holds also, among other things, when conditioning on mergers that follow exogenous downward pressure on the supplier's stock prices, suggesting that reverse causality is unlikely to explain the result. In contrast, the relationship vanishes when using rumored or announced but not completed integration events. Firms experience a substantial drop in sales when one of their suppliers integrates with one of their competitors. This sales drop is mitigated if the firm has alternative suppliers in place.
Download the latest draft

Measuring Image Concern

With Emeric Henry

Journal of Economic Behavior & Organization, Volume 160, April 2019, Pages 19-39
It is now well documented that individuals tend to change their behavior when their actions are observed by others. Yet there is no systematic way of measuring this dimension of preferences at the individual level. In this paper, we propose and validate a novel experimental game to measure individual sensitivity to social image. We document substantial heterogeneity in the level of image concern. We show that image concerned individuals tend to be less cooperative in a repeated prisoner’s dilemma, especially when their actions cannot be observed by others. Finally, we present evidence suggesting that the level of image concern is uncorrelated with observer characteristics, with one exception: members of ethnic minorities appear less sensitive to being observed by another member of a minority group.

Social Norms and the Prevalence of Hate-Speech: Evidence from Facebook

Work in Progress - More details to come soon


You can find my CV here.

Contact Details

Sciences Po - Département d'économie, 28 Rue des Saints-Pères, 75007 PARIS

jan dot sonntag [at] sicencespo dot fr