Interesting, I did a PhD in experimental physics in the UK and we only had two dropouts during my time. The group increased size from 8 students when I joined to about 25 when I officially finished (about 5.5 years later, long story)

What's more interesting, to me at least, is that I was one of the very few that didn't continue down the academic science path. Though to be fair most have since left it and I think only 5 have stuck with it, but still an impressive amount of postdocs