Part of your theory is a bit off. It is not money that may be having the Elderly landline based but technophobia, some older folks pick up on this stuff quickly some don't. I know of one Senior trying to save a phone number and accidently dialed 911! The local cops showed up in less than 5 mintues flat kudos to them, but I digress :-),
Yes many have dropped landlines and gone to cells to stay away from telemarketers, pollsters etc. Some still keep a landline as a backup, but caller ID allows you to screen out the telemarketers and pollsters. If you tell no one your cell, these annoying calls can't find you.
The bottom line is they are probably getting a very skewed picture, how twisted we will find out on the 1st Wends. of November.
FCC regulations, specifically 47 CFR Sec. 64. 1200, prohibit telemarketers from using an automated dialer, prerecorded messages or artificial voice to call any number assigned to cell phone service or any service for which the called party is charged for the incoming call.