Some people will look at this data and say "He's telling us all to carry .22s". That's not true. Although this study showed that the percentage of people stopped with one shot are similar between almost all handgun cartridges, there's more to the story. Take a look at two numbers: the percentage of people who did not stop (no matter how many rounds were fired into them) and the one-shot-stop percentage. The lower caliber rounds (.22, .25, .32) had a failure rate that was roughly double that of the higher caliber rounds. The one-shot-stop percentage(where I considered all hits, anywhere on the body) trended generally higher as the round gets more powerful. This tells us a couple of things...
In a certain (fairly high) percentage of shootings, people stop their aggressive actions after being hit with one round regardless of caliber or shot placement. These people are likely NOT physically incapacitated by the bullet. They just don't want to be shot anymore and give up! Call it a psychological stop if you will. Any bullet or caliber combination will likely yield similar results in those cases. And fortunately for us, there are a lot of these "psychological stops" occurring. The problem we have is when we don't get a psychological stop. If our attacker fights through the pain and continues to victimize us, we might want a round that causes the most damage possible. In essence, we are relying on a "physical stop" rather than a "psychological" one. In order to physically force someone to stop their violent actions we need to either hit him in the Central Nervous System (brain or upper spine) or cause enough bleeding that he becomes unconscious. The more powerful rounds look to be better at doing this.
One other factor to consider is that the majority of these shootings did NOT involve shooting through intermediate barriers, cover or heavy clothing. If you anticipate having to do this in your life (i.e. you are a police officer and may have to shoot someone in a car), again, I would lean towards the larger or more powerful rounds.
What I believe that my numbers show is that in the majority of shootings, the person shot merely gives up without being truly incapacitated by the bullet. In such an event, almost any bullet will perform admirably. If you want to be prepared to deal with someone who won't give up so easily, or you want to be able to have good performance even after shooting through an intermediate barrier, I would skip carrying the "mouse gun" .22s, .25s and .32s.