I'd have to say the West. Although there are regional hot spots, I'd guess there is a greater interest in the Northwest and the northern states, due mostly to the weather. Bowling (10 pins) never seem to have caught on in the Northeast, until you reach New York, New Jersey, and PA. (Maine, Mass, Conn, Vermont, NH, RI all seem hotter for skiing or candle pins.)
When snow and rain keep people indoors, bowling seem to attract them (Washington, Oregon, Minnesota, Michigan, northern Ohio, western NY, etc).
The location of ABC tournaments cities being 90% in the West is a constant source of irritaiton for me personally. Except for Syracuse and Knoxville, I have to take 2 airplanes to get there. This year it ain't gonna happen. (Sorry to get off topic.)
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"Just because you can do something does not mean you should do it."