GEV Shape Parameter

The shape parameter remained strictly negative for almost all countries and years in the study. If the shape parameter becomes non-negative, the fitted GEV distribution no longer has a finite upper bound. The shape parameter separates Fréchet, Gumbel, and reversed Weibull limiting distributions. Most countries showed an increasing shape parameter, implying movement toward loss of a finite upper bound. A flat negative shape-parameter trend would indicate movement toward a stable finite upper bound or wall of death.