Does CRM Training reduce accident rates?
Well, no it doesn't... Or rather, there is hardly any data suggesting it does, and yet there are mountains of data saying that improving technology reduces the accident rate reliably and continuously. (There's an odd factor affecting the Cirrus, a high-tech aircraft with an unexpectedly very high accident rate, but if you'll forgive me I won't go down that route).
Some CRM training, if expertly planned and well presented, provides interesting food for thought, and may confer benefits. Bad CRM training is far too common and probably achieves nothing. In any case, CRM is about behaviour, and it is very difficult indeed to change behaviour.
It is also very clear that a huge, self-serving and self-justifying, industry has grown up around this fluffy subject. Getting rid of that industry, or turning it into something which serves a useful purpose, is a big challenge... The fact that the regulator is infected with that industry's virus, more so in the UK than elsewhere, doesn't help.