Most modes of transport for cargo have indexes that measure performance and pricing.
For Air Cargo, there is CASS and one I will reference here as the World ACD.
The measure of air rates in the last twelve months has been a very volatile roller coaster. At first, it was the nearly complete shut down of world wide airlines because of Covid 19 protocols and fear of spread. Secondly, the cargo planes resumed flights as the limited air industry came online to move critically needs PPE. Other non-PPE cargo was moved at a lesser capacity and much higher air rate. As PPE supplies became steady, the standard air cargo products gained capacity options. Passenger planes finally put back into service have got us back to a near normal however, the year over year cost per kg is 75% higher in January 2021 versus January 2020.
All indications are that we will see costs stay higher than normal through the end of 2021 and possibly beyond.