This data, collected by Michael McDonald, an associate professor at the University of Florida, is one of the best sources for early-voting tallies across the country.

Collecting vote totals from 50 different state voting systems, plus the District of Columbia, presents a mammoth challenge, and in some cases, the data is not freely available to the public.

McDonald also stressed that the completeness of these figures hinges on how quickly the state office administering the election can process returned ballots.

The steps of “collecting these data are a real challenge, especially if the state doesn’t have a centralized reporting system,” McDonald said. He estimates a third of states don't have a centralized system that makes detailed voting data publicly available.

So while the numbers above are just a snapshot of some of the returned ballots so far, they form a definite baseline of how many people have voted and where.