Within-country heterogeneity

Another characteristic that merits some analysis is the heterogeneity in the ACRA policy in each country. Here we focus on differences between the protected routes of a country in terms of traffic density, route distances, prices and load factors. We use box plots to examine whether the protected routes in each country are similar. Box plots have the additional advantage of allowing us to determine the proportion of routes that lie at the extremes of the distribution (first and fourth quartiles) and the number of oudiers.

Figure 6.1 shows the box plots for route traffic density. The plots include the traffic densities on all routes, excluding outliers (in this case, routes with more than 200,000 passengers per year). The difference between the minimum and maximum values is greatest for countries operating thicker routes, and Colombia, France and the United States have a relatively greater number of oudiers. When we exclude these oudiers, the same three countries continue to present a high number of oudiers. Greece, Sweden, and the United Kingdom appear to be the countries that have the most homogeneous distribution of routes in terms of traffic density.

Figure 6.2 shows the box plots for route distance. France presents a high number of outliers, attributable to the long-haul Hights to its outermost regions. Once we exclude these oudiers (lower panel), India and Portugal become the countries with the greatest heterogeneity in terms of route distance, whereas Spain, Norway and the United Kingdom (with few oudiers) are the most homogeneous.

Figure 6.3 shows the box plots of prices per km. Here the marked heterogeneity presented by Norway and the large number of oudiers in the United

Figure 6.1 Box plots of total traffic on each route

Figure 6.2 Box plots of route distance

Figure 6.3 Box plots ot prices per km

Figure 6.4 Box plots of load factor

States are the most notable outcomes. When we exclude these outliers (i.e. the most expensive routes in Norway), Greece, India and Italy seem to be the most homogeneous countries. Finally, heterogeneities in terms of load factors are high (see Figure 6.4). The only exceptions here are Italy, Spain and to a lesser extent Malaysia and the United Kingdom.

In general, all 13 countries are characterised by a high degree of heterogeneity in at least some of the variables under consideration. In some instances, this seems to call into question the consistency of the policy given that different routes appear to receive support from the government and, presumably, obtain different amounts of subsidies per passenger.