NTSB statistics (GA only) show that there are roughly 430 engine failure accidents per year in the US GA fleet of about 150,000. This equates to 0.2%. To normalise that against number of hours flown, it works out at 1 per 50,000 flight hours or something like that.
Apologies for referring so far back (this thread has been growing fast), but here's a question I was pondering the other day while reading "The Killing Zone"... Presumably not every engine failure leads to an accident, as I assume all that PFL training I've done (and I like to practice it every so often, even now that I'm licensed to kill myself
) gives me half a chance of actually landing the plane without damage.
So I'm guessing that actual incidences of engine failure are quite a bit higher than that... anybody care to guess how frequent?