Resolves as a percentage equal to the voting-eligible population turn out rate (total ballots counted).
Market closes on election day, resolves when the first estimate becomes available from a credible source (my criteria, open to discussion).
I will resolve if https://www.electproject.org publishes an estimate. For reference they have 66.6% for the 2020 so this market would have resolved with 67% for the 2020 election.
If a month after the election there is no estimate I will calculate it using as numerator an estimate of total voters (again from I believe is a credible source) and using as denominator 258,676,000 (which is my estimate of voting-eligible-population).
I'll just this source which is what Wikipedia is using at the moment: https://www.thegreenpapers.com/G24/President-Details.phtml
Total votes there were 155,627,481. And using the denominator from the description gives 60%.
Alternate source for eligible voter count data: University of Florida Election Lab
For example, they calculated 244,037,811 for 2022 and 259,323,882 for the 2024 primary.