None, and I'll go far beyond that. I don't respect people who own guns for protective purposes. Certainly not the point I'd ever take their advice on anything. I view the issue as one of the great litmus tests on basic common sense. Seriously, how could anyone need a survey? If a deadly weapon is there 24/7/365, society loses. Pure math.
You've got to shake your head at posts asserting they "talked" to their son, as if that has a fleck of value compared to sheer availability. I guarantee one shooter after another was "talked to" at some point.
Once in Las Vegas I was scheduled to move into an apartment with a friend. First day in the place I went into his room and there was a handgun on his nightstand. I expressed my feelings and moved out before spending a night in the place.
As other have pointed out, intruders are concerned with noise and light. Home alarms systems are effective, along with dogs.
It could not be more meaningless that some people have been saved by owning a gun. Nothing is zero. Nobody is claiming zero. I'm sure there's an example of a bumbling fool who on his first day of owning a gun successfully pulled the trigger with his eyes closed and pointing in the wrong direction. The net benefit is toward fewer guns, not more guns, and it's not a close call.