This subject is a difficult one for which to get any definitive answers because such statistics are gathered specifically dealing with such things.
Now, of the homicides reported by LE, where private citizens have been determined to have committed a justifiable homicide? (The killing of a felon, during the commission of a felony, by a private citizen.)
The FBI's UCR data contains statistics of what's reported to them by LE. This data can be found by scrolling down the page at the following link, as well as some other data:
http://www.fbi.gov/about-us/cjis/uc...o-law-enforcement/expanded/expandhomicidemain
You'll find this data specifically contained within Table 15 on the above page:
http://www.fbi.gov/about-us/cjis/uc.../crime-in-the-u.s.-2010/tables/10shrtbl15.xls
It can be contrasted with the number of justifiable homicides by LE in Table 14, BTW.
While you'll notice there's a breakdown available of the weapons used by civilians in the justifiable homicides, the number of shots fired isn't listed.
I don't tell folks what I think they should carry in the way of firearms lawfully carried as dedicated defensive weapons. I can only make such decisions for myself.
How I make such decisions for myself is based on a variety of considerations, but mostly it involves the use of my experience & training, and assessing the potential risk I perceive to exist for whatever I'm going to be doing, wherever I'm going to be doing it.
This typically results in me choosing to carry a variety of handguns, but that's mostly because I own, train, practice & qualify with a variety of them (since I've been a firearms instructor for more than 20 years). I could certainly "get by" with fewer, or only one, if need be (another subject).
Suffice to say that depending on the day, my planned activities and where I plan to engage in them, as well as my inclination for even being armed that day, I'll carry a 5-shot .38 Spl or .357 Magnum, or a pistol with a magazine capacity of 6, 7, 8, 9, 10 or 12 rounds. The pistol caliber will be either 9mm, .40 S&W or .45 ACP. Yes, I typically carry spare ammunition in speedloaders, speedstrips or magazines.
Now, that's what I've decided is appropriate for me, depending.
Do I anticipate the possibility of more than a single attacker? Sure.
Does it keep me awake at night? No.
Will the potential sometimes influence my choice in which weapon I choose? Yes, but only so far as it becomes a factor in my regular daily risk assessment and decision of whether I should be armed that day, which varies.
Do I claim to be able to predict the future? Of course not. However, neither am I willing to walk around armed like I'm going to be working a high activity patrol beat and responding to calls of violent crimes in-progress all day or night, either.
That's me and my thoughts, and how they've come to influence my choice when I was carrying an off-duty weapon and now that I'm carrying in retirement. Suit yourself.
I'd think it reasonable to expand such concerns to include the other factors I've often mentioned in such thread topics, though, meaning I think it's prudent for an individual to give some attention and consideration to their own knowledge of the laws involving the use of deadly force and what's involved in lawfully carrying a handgun for defensive, as well as their experience, training, skillset and mindset ... and chosen equipment (holster & weapon). It's just a handgun ...
Remember, you can never call a bullet back once it's fired. Give some thought to being able to accurately & effectively use whatever ammunition is being carried, since there are serious potential consequences for hitting things which aren't the "intended target".
And, yes ... sometimes I'll wonder at folks who have decided to carry more handguns, magazines, speedloaders and ammunition on their person as private citizens than I used to carry when I was working in LE. It's not my decision to make for them, though. I do, however, sometimes wonder about their level of training & skill, as well as their experience when it comes to functioning under stress.
Then again, I wonder about more folks in that regard as it pertains to their ability to operate a motor vehicle on any given day.
Just my thoughts.