Here is another outstanding video in a question and answer type of interview. Outstanding information. Pretty in depth but it helps a person understand how things work, as best it is understood to date. Might actually want to watch this one first as the audio is much better and easier to understand him with his accent.
Edit: now I am confused. This may have been the presentation that had the statistic I quoted. At any rate it is a good presentation. I'm just sorry I did not get the link included in the original post.