Replication data for: War, Technology, and Change: The Ratchet Effect and System Unification

I formalize and test the ratchet effect, a theory that variation in the offense-defense balance and the cost of war leads to increasing geographic size of units (e.g., states, empires, and superpowers) in the international system from the interaction of the offense-defense balance and the guns-and-butter tradeoff. When the cost of war is high, the status quo obtains. When the cost of war is low, change depends on three levels of the offense-defense balance: 1) when offense is dominant, units transfer few resources to subunits and expand through conquest; 2) when defense is dominant, units transfer substantial resources to subunits in order to consolidate internal cohesion and forestall secession; and 3) when neither offense nor defense is dominant, weak units transfer resources to powerful units (salami tactics). Oscillation of the offense-defense balance over repeated rounds leads to a punctuated equilibrium of unit consolidation and increasing average unit size over time, ending in a stable system unification. I find quantitative and qualitative evidence for key features of the ratchet effect, including: an increase in the size of states; a punctuated equilibrium; and, using multiple imputation, matching, and two-stage parametric models on data from 1816 to 2000: 1) offense-dominant military technology increases the probability of territorial change; 2) given territorial change, offense dominance leads to a relative increase in the territorial size of states; and, 3) in nonconflict years, middle ranges of the offense-defense balance lead to lower levels of territorial increase. Historical anecdotes provide causal evidence, and indicate that the relevant units of analysis are a product of the very expansion for which they function to obscure. These units of analysis have similarities that are the basis of defining a single historically comparable unit of analysis -- the power unit.