It's really difficult to define with perfect certainty the when/what/where/why of it all.
What we do know is that there is roughly about 35,000 deaths per year in the US.
-Of this 35k, about ~61% is suicides.
-About ~35% is homicides.
-soooo, less than <5% is a mixture of LEO's (usually around ~500), accidental (usually around ~500), etc.
-It has been estimated that about 100,000 incidents are reported on average due to ALL firearm involvement.....this includes accidents, shootings/woundings, good/bad usage, suicides, defensive use, homicides, etc.
-It has been estimated that anywhere from 200,000 to 2.5 million incidents occur where a firearm was used in defense of something. This number is very hard to calculate. We do know that the FBI has noted that ~60-80,000 police reports are filed each year noting defensive firearm usage.......however, they freely admit that most defensive firearm usage is NOT reported. Many, many, many people just don't contact law enforcement when something happens.....and a huge portion of law enforcement either doesn't or can't file reports even when they occur.
But, like in life, everything is situational. I remember growing up waaaaay out in the sticks. We used to joke that "you don't find our front porch by accident. Our driveway was so long that momma has time to make a pot of coffee before you pull up.....etc, etc." If someone wanted to try a home invasion, a person would have to hoof it in a good distance in the dark......over fences and forests......not disturb the cows, horses, chickens, dogs.......avoid every creaky board on the front and rear porches.....not trip the alarm.....etc. It would've been more difficult for the Average Joe criminal to undergo a home invasion than it would be kick in the door of the average trailer park home or apartment......
But as they say, "don't bring a knife to a gun fight." Whether your chance of defense is very little or a decent amount, you're better off with a gun than without one when it comes to home defense.