Data and Statistics are always fraught with confusion.
It begins with how the Data is compiled...definitiions, tabulating, and calculating....all can result in Apples and Oranges comparisons.
Look to the American Helicopter EMS studies one time....usually running years behind time and filled with some real ambiguities.
As to language....Rotorbee does better in his second language than I do with my second.....my first being "Down South" and the second being American English.