Consider the following point.
The .40 exists as a result of an event called "The Miami Shootout" where some FBI agents lost a gunfight with some bad bad guys who fought through multiple gunshot wounds.
What came out of the aftermath of this shootout was the belief that the .38 revolvers and 9mm pistols that the FBI agents had were anemic and underpowered.
This led the FBI to make a paradigm shift, and they first adopted a 10mm pistol, then had S&W to develop a new round that became the .40 S&W. There was a s**tpile of money and expertise plowed into this effort.
The round was touted as THE solution to the underpowered .38/9mm. 45 lethality in a 9mm style pistol, or so they said.
This story indicates otherwise.
So while this is a statistical abberation, it's no more of a statistical abberation than the Miami Shootout was, and that event was huge.
I think it's evidence that the 40 is a solution to a problem that really never existed, and it's real world stopping power is not significantly better than a 9mm.
I suspect that the 40 was merely an exercise in marketing for gun and ammo companies....much like the new wonder cartridges they introduce for hunters every couple of years.