Since the high level of accidents in the 70s we have had:
- New generations of aircraft
- Better automation
- TCAS (which is generally there to protect from human error, but mainly ATC)
- GPWS/EGPWS
- The CRM revolution
As far as I'm aware without the ability to crunch MORs, NASA ASAPs, company safety reports &c we only really know that the accident rate has decreased, and that a number of high profile accidents have involved human failings.
I am interested in how one can ascribe a certain percentage of the accident rate reduction to different factors above and others I have not mentioned. I would welcome links to studies that attempt to do that.