I find it hard to believe that Rav Rechnitz did not do a survey of the type you describe. In Los Angeles, the community is small enough that I think you could do this survey just by looking at graduation pictures and asking the local Yentas what happened to this one, what happened to that one, etc.
You can’t bring a raya from oot to the overall numbers. A disproportionate number of bochurim are on the east coast, specifically tri-state area, and all else being equal (on “paper”) would prefer not to travel to meet a girl.