Lots of people have debated this 2.5 million claim. But one part of the argument I've never seen is this.
Some percentage of DGU incidents is not defensive and legitimate. If the bad guy is dead, it's easy for the shooter to shade the circumstances enough in his direction to make it legit. If the bad guy lives, people tend not to believe what he has to say, he is a bad guy after all.
This goes double for those supposed brandishings in which the bad guy runs away.
So, I take the lowest estimate out there, which is about 50,000 or 60,000 and cut it in half. That's what you've got for true DGUs, and that corresponds perfectly with what we read in the news.