Critical dynamics govern the evolution of political regimes

Abstract

The emergence and decline of democratic systems worldwide raises fundamental questions about the dynamics of political change. Contrary to the idea of a stable endpoint of liberal democracy, recent backsliding towards less democratic regimes highlights the non-stationary nature of regime evolution. Here, we analyse the historical trajectories of countries within a two-dimensional regime space derived from the principal components of the Varieties of Democracy dataset. We observe weakly non-ergodic dynamics unfolding in an effective landscape characterised by sparse and shifting basins of stability. Step sizes and sojourn times characterising this dynamics follow heavy-tailed distributions near the critical regime, in which mean values appear to diverge. These facts point to the intermittent and heterogeneous nature of the regime change dynamics. A continuous time random walk model reproduces the dynamics of the three most recent decades with remarkable accuracy. Together, these results suggest that some aspects of political regime evolution follow universal stochastic principles, while remaining punctuated by unique historical pathways.

Figures (8)

• Figure 1: All country-year observations in the PC1-PC2 political regime space. Selected examples indicate regions typically associated with democratic, autocratic, and hybrid regimes. These labels are illustrative and do not imply discrete regime classifications.
• Figure 2: Representative regime trajectories in the two-dimensional political regime space. Coloured symbols show selected country trajectories over time, superimposed on all country-year observations (black transparent dots). Inset: time-averaged mean-squared displacement (TAMSD) for the same countries.
• Figure 3: Step size and sojourn time PDFs in regime space. Histograms show the PDFs of annual step sizes in PC1 and PC2; inset shows the normalised sojourn time PDF. Dashed coloured lines indicate maximum-likelihood power-law fits using a representative crossover point $\mathrm{PC}_c=0.1$ (black vertical line), with estimated exponents reported in the panels. Grey dashed lines indicate the range of crossover points considered.
• Figure 4: Representative examples of large regime transitions in the PC1-PC2 political regime space. Arrows indicate one-year displacements associated with well-documented episodes of democratisation (a), autocratisation (b), military coups (c), and revolutionary change (d). These examples show that large movements in regime space correspond to substantive institutional ruptures, providing qualitative grounding for the heavy-tailed step-size statistics analysed in the main text.
• Figure 5: Mean first-passage times (FPTs) in the regime space for successive 30-year windows. Warm colours indicate longer FPTs and thus greater local political stability, corresponding to prolonged residence near a given institutional configuration.