Nearly 22 million Americans vote early in the 2920 US presidential election. (Photo: Reuters)

The 22.2 million ballots submitted as of Friday night represents 16 per cent of all the votes cast in the 2016 presidential election, even as eight states are not yet reporting their totals and voters still have more than two weeks to cast ballots.

Michael McDonald, a University of Florida political scientist who has long tracked voting for his site ElectProject.org estimated that Americans' rush to vote is leading election experts to predict that a record 150 million votes may be cast and turnout rates could be higher than in any presidential election since 1908.

He said around 70 million votes will be sent to voters prior to November 3.