I wonder how many dead people voted?
There are sporadic reports of people who registered to vote in the 1960s and still do - meaning lots of 100+ year old voters.
This is from 2012
North Carolina Finds 2,214 Registered Voters over the Age of 110
http://www.breitbart.com/big-government/2012/10/23/no-car-finds-2-214-registered-voters-110-years-of-age-older/
This is for Pennsylvania
http://www.theacru.org/more-than-100-years-old-and-still-voting/
So the short answer is - we don’t know, but we know they do exist.