FROM DAN USA
To many people who drive a car every day, running out of fuel may seem improbable, but according to AAA it is a daily occurrence. Likewise, ineffective breathing-gas management while diving is a recurrent problem. During peak season, DAN Medicine speaks with at least two divers every week who have concerns about having made a "rapid ascent" after finding themselves low on or out of breathing gas. Although the incidence of fatal injuries is very low, about 41 percent of dive fatalities involve insufficient breathing gas as the trigger that led to other harmful events and, ultimately, the death of the diver. Drowning is the leading cause of death in these situations.
Whilst there is a perception by some that the AAS is never needed. The BSAC report had 133 recorded cases in 2018, (some may or may not have been for OOA incidents, but it can be assumed that breathing gas was compromised in oneway or another). I accept by some that he BSAC data is seen as an unreliable.
DAN also states a minimum of 2 divers per week (during the season) contacting them due to medical issues after OOA rapid ascents. These according to DAN are attributed to out of air (gas) issues. The DAN information didn't break the information down into AAS ascent or CESA ascents. However, the DAN data is only for those that reported a medical issue to DAN. It does not include data from ascents that may have been successful with no complications, or for those who don't have DAN cover. This information appears to be USA centric, rather than UK centric.
Whilst all here are perfect (with the exception of myself).
The Data from the two organisations that I know collect data [1], DAN and BSAC, (which may or may not be 'reliable',) seems to show that Gas issues happen reasonably regularly. One would reasonably assume (?), such issues are more likely to occur in holiday destinations where there are more 'divers' who probably dive infrequently, or have a small number of lifetime or annual dives.
Whilst the overall numbers may be small in comparison to the number of dives annually, they are significant enough to be of concern to those providing diving services at holiday destinations.
Diving fatalities are (thankfully) very small in comparison to other causes of (sports) deaths.
BSAC and DAN records represent a very small percentage of those actually diving. DAN relate specifically to those members calling on them for medical assistance. The BSAC relate to its membership. mainly in the UK. So neither are truly 'representative' of the 'diving population'.
DAN source
[1] I have only quoted DAN and BSAC because I know these two organisation do record diving incidents, and I am or have been a member of both. There may be others, no slight is meant by me not referring to these agencies.