It's probably going to be quite a bit more than 4 million. There are still several heavily blue states that have a lot of votes left to count.

California, for example, has only counted 77% of their votes. New York has counted 84%. Illinois has counted 89%.

I just caught the end of some discussion of this on NPR. Based on the number of votes left to count in the various states and how they are expected to turn out, there is a good chance it will end up at around 8 million.

Also, it probably makes more sense to look at it out of the number of voters, or the number of people who could have voted, rather than out of the whole population.

It's currently 4 million of 145 million votes, since not all 330 million people are voters, and that number will go up since the outstanding votes are in large, overwhelmingly Democratic states.

According to Nate Silver:

> Biden is likely to wind up with one of the higher percentages of votes as a share of the U.S. population that we’ve seen in a long time

Referencing this tweet, text copied below as well https://twitter.com/jtlevy/status/1324408585590329345

[credit: Jacob T. Levy]

  vote share * turnout

  Reagan 1984: 53.3*58.8= 31.3%

  W Bush 2004: 50.7*56.7=28.7%

  Obama 2008: 52.9*58.2=30.8%

  Biden 2020, estimated: 51*66 = 33.7%

  counted so far: 50.5*60.3=30.4% (as of 2020-11-05)