Table 1.

Cross-validation results for out of sample prediction of CCs across all world regions

 Predicted CC Overall ρ2 Polity population 0.84 Polity territory 0.76 Capital population 0.71 Levels of hierarchy 0.60 Government 0.53 Infrastructure 0.62 Information system 0.59 Texts 0.73 Monetary system 0.53
• Prediction accuracy is measured with prediction ρ2 (SI Appendix, Table S2). Overall ρ2 values are calculated as an average of the ρ2 values weighted by the number of polities from which they are drawn.