Figure 4

Assessing change in mobility trends over time. The Spearman’s rank correlations shown in subgraph (a) allow to infer whether a trend is monotonously increasing, decreasing, or stable/fluctuating. The cumulative distribution of the population-size-adjusted difference between the 2016 and the 2011 trend value shown in subgraph (b) illustrates the sizes of the changes. Negative values denote decreases, positive values denote increases. A value of 0.025 for instance denotes an increase in air passenger travels that corresponds to 2.5 percent of the sender-country population. A small number of extreme outliers are excluded