In San Luis Obispo, CA the sheriffs department has a program where minimum security inmates recondition old bicycles to give to children in need. They rebuild hundreds a year I guess. There is a guy in LA who does the same thing except he sells them for a few hundred each out of his garage. I think many of the bikes come from estate sales, yard sales, and such. Anyway, my point is, though 'm not sure where all these bikes are found, there must be millions of old bikes that could ride again.