Economics and Finance Seminar: Etienne Le Rossignol (Namur University)
02 April 2026, 12:00-13:15
In-Group—Out-Group Trust: Origins and Consequences
Why do societies differ in the breadth of trust they extend beyond the in-group? This paper argues that historical mobility, specifically, the ecological and institutional demands of transhumant pastoralism, shaped long-run variation in the scope of trust. Combining global data from 104 countries, individual-level surveys, and within-country evidence from Kyrgyzstan and Africa, we show that ancestral reliance on transhumant pastoralism predicts higher trust in in-group members relative to out-group members. We then uncover the mechanism using a newly assembled Atlas of Transhumance Routes: the effect is significantly stronger along flatter, more “horizontal” routes that historically generated recurrent encounters with other pastoralists under weak external enforcement. These routes intersect more ethnic boundaries, and the intensity of such encounters amplifies the transhumance-trust relationship, especially where interactions involved competing pastoral groups. A natural experiment, the 2011 partition of Sudan, which abruptly obstructed long-standing migration corridors, shows that conflict rises sharply along historical routes once mobility becomes constrained. Finally, we show that a narrower scope of trust constrains organizational hierarchies: firms in historically pastoral regions rely less on objective promotion criteria and remain smaller. Together, the results highlight the enduring cultural and economic consequences of historical mobility.
