[themckman]

For a little context, some rough voter totals going back to 2000 (in millions):

    2016: 126
    2012: 129
    2008: 131
    2004: 122
    2000: 105

While, certainly, there were less votes cast than the last two elections, it doesn't appear to be a record low.

Edit: Sources are Google for 2016 and Wikipedia for the rest.

[AnimalMuppet]

Don't forget to factor in population growth (above 18 years of age) from 2000 to 2016. Is it enough of a factor to make 2016 the record low? I don't know.