[Nich]

so the effectiveness of seatbelts is not determined by number that are injured/die, but rather number that are not injured/die (who otherwise would have if not for big seatbelt) Ok, fair point.

My point is primarily for any given month of car accidents, as a proportion of the population of NSW the 53% who wear seatbelts should not represent 78%, 53%, and 75% of the injuries, hospitalisations, and deaths respectively.

But you CAN account for survivorship bias in the NSW data because there's 47% of the NSW population who wear no seatbelt (or 1,2 seatbelts) and they represent less injury, ICU, death compared to 3+ seatbelt cohort.

I think if anything the NSW reports show that 3+ shots just have more car accidents than the rest of us.