I wonder how the move to DSL and Cable Modem has decreased the demand for lines for modems and fax machines, and the demand for lines for modem lines (or T-1s) at ISPs? For a while there, there was a tremendous peak in demand for POTS lines (and POTS minutes). A fair amount of this was served by CLECs, but I think ILECs handled a fair amount of it. Between that peak, competing wired services (VoIP over DSL and Cable Modem), and substitution of cellular for wired, I can see a drop in demand for POTS. I think the FCC publishes figures on POTS usage, but have not really looked at them.
Harold