Burden-Sharing in Action: Spatial Dynamics of Defence and Humanitarian Spending Among NATO and EU Member States

Russia’s full-scale invasion of Ukraine has profoundly tested the resilience of NATO and the EU, prompting unprecedented levels of military and humanitarian assistance. This paper examines how member states of these organizations have responded to the geopolitical disruption, with a particular focus on the spatial dynamics of aid provision. We employ spatial econometric analysis to investigate whether, under intense geopolitical pressure, countries exhibit “free riding” or “following” behavior—patterns that reflect both disruption and resilience in collective action across NATO and EU members. Relying on more fine-grained (monthly and quarterly) data from the Ukraine Support Tracker, we identify spatial interdependencies in defence and humanitarian spending. In particular, we spotlight certain key reference groups (e.g., neighboring states and major allies) that seem to influence how individual countries allocate aid. Our findings indicate that heightened geopolitical threats can alter traditional spending habits, challenging established theories of free riding within NATO. These shifts also highlight the alliance’s capacity—at least in the short run—to uphold effective collective action, even as burden-sharing remains uneven more generally. By uncovering these spatial patterns, the paper underscores the importance of the “following” behavior in mitigating disruption and reinforcing resilience within international organizations. More broadly, our results enhance understanding of how institutions like NATO and the EU adapt to external shocks, offering new perspectives on strategic behavior and the distribution of burdens that underpin collective action in the 21st century.