[rrdharan]

This Planet Money episode attempted to tackle that question: http://www.npr.org/sections/money/2014/10/21/357629765/when-...

Their tl;dr answer is that video games happened, and they were marketed exclusively to boys; that's what created and drove the cultural rift.

[ci5er]

Thanks for that link. My original sighting of the phenomena used the exact same graph, but made no attempt at being explanatory. I have since then, been searching, but failed to re-find a copy of that graph to stick into my files. Now, thanks you you, I have! Thanks!