While I should have the current statistics off the top of my head, I don't.
Since there are quite a number of officers are killed with their own firearm, weapon retention is now part of the academy (we had only a cursory introduction when I went). I volitionally went to a Safariland Level SS III holster. Rob pointed out a problem with some of these holsters - some folks can't get their guns out or train with the snaps undone. In a real life situation, when they go to draw, they forget to unsnap the holster! Train as you plan to fight they say.
A bit of digression here. My semi-auto pistol instructor had one of those Level III holsters and he cheated. Got into a gunfight and felt jolt of pain in his crotch. He cried out to his partner, "I'm hit!" His partner is engaging the BG of course while my instructor keeps tugging at his gun. When the fight is done and over, (the good guys win), the instructor checks himself and finds no holes. He then realized that he didn't break the 2nd snap on his holster. What happened is that when he drew, because of the keepers, his trousers rode up on his waist, tugged at his crotch, and thereby causing the cramp/pain in his crotch. He learned to practice and that example is one which I tell my shooters today. Indeed, I tell them to practice drawing at home for about 1,500 times to get the muscle memory reflex down nice and natural. To simulate an injury, I challenge the (slimmer) officers I challenge to draw from behind their back with their weak hand. I have another technique for a pot bellied officer, but enough digression.
Mind you, like Rob says, bad guys read the gun rags too and know how to remove the gun. Some openly practice it in the prison yard.
While officers are taught to keep an arms and a half length distance from a suspect, that goes out the window when you're involved in a knock-down, drag out fight or a wrestling match - both which should be avoided. Natuarally, this is easier said than done.
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Vigilantibus et non dormientibus jura subveniunt