I can’t speak to this subject except for what I know. Having grown up on Chicago’s north side really close to Wrigley Feild I can tell you that you can’t stand on any given street corner near Clark and Montrose and swing a dead cat (sorry PETA) without hitting at least two mom and pop joints that sell really thin crust pies. One that comes immediatly to mind is Angelo’s on Montrose near Albany Ave. The only time I was near one of them deep dish monstrosities was when my in-laws flew into town from Detroit. I was not impressed.