That's me, to a T. I noticed that trend - i guess it fits about right. The game really didn't start to take off in popularity until then - and that is the age when the first generation who grew up on the game would have started to notice it. While there are players who started earlier, the game was really basically unknown then - not until the basic set did it start to really take off.
It will be interesting to see the graphs of ages and start of play in another 10 to 20 years - and see what effect 3E had overall.