I'd suspect something in the 1e, B/X, 2e era for exploding it, also 5e for the ridiculous reach it has had.

I'm not sure 3e really expanded the market significantly. I think it maintained the market well, but I don't think it gained much ground.

Quote Originally Posted by KorvinStarmast View Post
B/X and it's followers were sold in toy store and game stores.
Get them while they're young.
I got my copy of Moldvay Basic in a WALGREEN'S.

I got a number of my AD&D books from SEARS.

In those days, D&D had retail penetration it doesn't even have today.