Quoting from a necro thread (2013) but Ben m's reasoning seems sound to me.
My highlighting.
My highlighting.
Yes.
It's easy to see, in the available numbers, that chasing-off-dangerous-home-invaders is NOT common. Why is that? Because 60% of homes are not armed.
Imagine a world where "defend your home with a gun" is 100% effective. Imagine there are 10,000 attempts to mount deadly armed home invasions. Well, 3,300 of those would get foiled---those would wind up in the NRA's anecdotal-evidence file---but 6,600 would be hitting unarmed homes and result in harm to the occupants. And "harm to the occupants", unlike NRA-newsletter brandishing-incidents, does get recorded and counted reliably.
See? If you look at the number of actual deaths in home-invasion-robbery incidents, the number of murderous-invasion-averted-NRA-anecdotes is *no greater than* 1/2 of this number.
OK, the National Violent Death Reporting System can give us those numbers for 16 states. Let's look at 2009 data:
Population of reporting states 81,587,293 (about 1/4 of the US population)
2,579 total gun homicides.
137 total homicides by strangers (!)
49 of which occurred in homes (not necessarily the victim's!)
Multiply by 4 to get approximately nationwide numbers.
There were only ~200 successful in-a-house murders-by-strangers in 2009. Total. A tiny number. Let's be generous and say those were all home-invasion robbery-murder attempts.
There cannot have been---if gun-self-defense were foolproof, in a country where 2/3rds of homes are unarmed---more than 300 home-invasion-murder attempts in 2009. Therefore, there are fewer than than ~100 true robbery-murder-averted anecdotes in 2009. There's your "guns save lives". Legal-gun-owner-home-defense saved fewer---probably far fewer---than 100 lives in 2009.
Heck, there were ~350 accidental gun deaths in that time. There were ~50 accidental gun deaths of children under 14.
That's why I've said this before and why I will keep saying it. Keeping a gun at home to protect you from home invaders is utterly, horrifyingly wrong. Dangerous home invasions are preposterously rare, as non-gun-owners have proven by not dying in home invasions.