Measures for characterizing settlement patterns, population distribution and accessibility in Africa at administrative level 1.

A. Percentage of land surface concentrating 90% of population. This measure emphasizes provinces of highly focal population distribution (in dark) and those where the population is more dispersed (in white). B. Clark and Evans aggregation index of settlement point patterns (<1 suggests clustering; >1 suggests ordering). C. Average per-person travel time to nearest settlement with more than 50,000 people, calculated by combining the global map of accessibility [25] with our detailed population distribution dataset. D. Skewness of the average per-person travel time across the population. A high skewness (in dark) suggests that people are concentrated in cities, whereas a low skewness (in white) suggests that a high proportion of population resides in relatively inaccessible areas.