I made this graph today showing the real value per tonne of New Zealand exports and imports by air freight. The real values are calculated using the CPI.

Interesting that the value of imports per tonne are about twice those of exports. A lot of air-freighted imports are probably pharmaceuticals. Also interesting that the real value of exports per tonne has increased about 5x over the past 20 years while the value of imports has fluctuated but not really increased.