Sounds like an extrapolation from the NYPD SOP-9 reports. Ya gotta remember, though, that New York City has 8 million people on a small island. LAPD studies, when they put them out, indicated a bit longer distance, and Federal Law Enforcement Training Center indicated a higher output of rounds per participant, with a nationwide Fed study.
All I can say is, don't base your defensive plan entirely on statistics. Statistics imply norms. The very fact that you need to resort to a gun indicates that you're experiencing a deviation of the norm, and there doesn't seem to be a category for "statistically average deviation from the norm."
If anyone tells you otherwise, remind them that you're dealing with life and death, and they are dealing with numbers. The whole defensive gun thing is about deviations from norms, I'm afraid...
Wishing I could have been of more help in simplifying an inherently complicated question,