Impressive stats, but an interesting analysis. Like all economic analysis it's a bit superficial.
With growing travel between countries by air, so more ppl are seeing other places, and the world seems a smaller palce to do business in. As such, with growing volumes of freight and business between countries, alternative freight routes become available, increasing the alternatives to air freight as reliable and fast.
It make sense that alternative freight would increase exponentially beyond PAX growth in air travel as pax growth gets cheaper.