I checked a bunch of them at random (~25). Most I couldn't find a birth month for and I didn't guess. The 4 I did find were registered but had not voted.
UPDATE: I stopped being lazy and started guessing the birth month. I got a lot of hits. Almost all the ones I tried were registered but did not request, receive or return a mail in ballot. Only 1 requested a mail in ballot but there was no date of return (I suppose they didn't return it). Also, I did not verify if these were people still alive (they'd be ~100 years old).
TL;DR: lots of registered people but I saw no returned ballots in my sample of about 25.
I checked a bunch of them at random (~25). Most I couldn't find a birth month for and I didn't guess. The 4 I did find were registered but had not voted.
UPDATE: I stopped being lazy and started guessing the birth month. I got a lot of hits. Almost all the ones I tried were registered but did not request, receive or return a mail in ballot. Only 1 requested a mail in ballot but there was no date of return (I suppose they didn't return it). Also, I did not verify if these were people still alive (they'd be ~100 years old).
TL;DR: lots of registered people but I saw no returned ballots in my sample of about 25.
Could you verify they had not voted? Or merely that they had not requested an absentee ballot?