One BIG thing most people forget....
Is that the eradication of lead from pipes and paints and gasoline has reduced the violent tendencies of people and so we have a drop off of violent crime.
Lead poisoning is what many believe made the Romans so aggressive and so brutal. They used lead, because it was a metal they could work with, because it was pliable in almost every aspect of their lives.
Here in this country, one could look a NYC, which was undoubtedly shown as one of the most violent city in the USA. Most sociologists claimed that the crime rate was due to poverty and loss of hope while being surrounded by the riches of a capitalistic society. Of course that is one major part of the puzzle. But it was the removal of lead from so many things we used on a daily basis that scientist now look as a major cause for that drop in crime.
And then there was Giuliano who just happened to be there at the right time as the age of people who are most likely to turn to violent crime, men between te ages of 15-25, was the first generation to have most of the lead taken out of their environment.
Add to that the legalization of abortion and the pill both allowed women to make a choice concerning how and when they would become mothers made for a lot less kids who where shunned because they were not wanted.
It's fascinating to me all the different tangible reasons for the drop in crime rates. To me, this proves that we are all a product of our environment.
This is a link about what caused the steady drop n crime that started in the late 1990's and continues till this day...
In the 1990s, after decades of relatively steady increase, crime rates in the United States
began a sharp and surprising decline. Researchers have investigated many possible explanations
for this decline. Most recently, Levitt [2004] argues that the decline in crime in the 1990s is
primarily explained by increases in the number of police, the size of the prison population, the
waning crack epidemic, and the legalization of abortion in the 1970s. This paper argues that the
removal of lead from gasoline in the late 1970s under the Clean Air Act is an additional important
factor in explaining the decline in crime in the 1990s. The main result of the paper is that changes
in childhood lead exposure are responsible for a 56% drop in violent crime in the 1990s.
http://www3.amherst.edu/~jwreyes/papers/LeadCrimeNBERWP13097.pdf
There was a NYT article that I posted some time back in the 00's that first brought this to my attention.
Anyway, it just gives us another way how environment can really have profound effects on us all in ways we never see.
= new reply since forum marked as read
but I think possibly back in the 1960's. I'm not even doing a quick Google search on this, but apparently all wall paint contained lead through the 1950's. It was phased out starting around 1960 or so.
Apparently, very young children tended to eat the paint chips that fall off walls (although I've NEVER seen such paint chips in any place I've lived in) and ingesting such things is Very Bad. Leads to lower IQ, among other things.
Maybe the old lead-based paints simply tended to chip in a way other paints don't. 
