Your witty Slashdot one-liner tells me every time you see stats, you just say that. RTFA
This exact correlation can be found to any substance that we used in the 60's but banned later and was eliminated in the 90's: DDT, asbestos, CFCs etc. Hell I bet you would find this correlation in the decline in radio listeners and a rise in the quality of American made cars. They didn't prove anything. If they compared blood samples from the prison population and the general population, during that time period, and found that the prison population had higher levels of lead then they would start to have convincing statistics. This is just a guess that maybe these numbers mean something. I would say the correlation is strong enough to warrant further investigation. Until then it is just a guess that maybe somehow lead and crime were related in this time period.
The Tao is like a glob pattern: used but never used up. It is like the extern void: filled with infinite possibilities.