So I became curious about voting patterns, if any, and tried to put together a consistent set of population and presidential election voting numbers for the recent past. I could not find a data source that had estimates of the age 18 and over population, so my population data is age 16 and over. (That shouldn't make much difference.) And I looked at the percentage of the population that voted, back to 1948, because I was curious about the effect of extending the franchise to 18-year-olds (1972 was the first presidential election in which 18, 19, and 20-year olds could vote. My expectation was that there would be a noticeable drop in the percentage of the population age 16 and over in 1972, with the voting percentage rising at least for a while. Here are the numbers:
% of Population Age 16 + Voting
Voting had been edging downward following the 1960 election, and, contrary to my expectations, it continued to fall through 1980 (or, really, through 1988, as the small bump upward in 1984 didn't constitute a reversal in trend). The jump up in 1992 is not a particular surprise, given the interest aroused by Ross Perot's strong support. The jump in 2004 is a bit surprising, given a reasonably popular incumbent and a not terribly exciting challenger. What is striking is that the 2016 election has had the lowest second lowest turnout since 18-20 year-olds got the vote.
I'm not a political scientist, I'm an economist, but the low turnout this year seems surprising (in one way), but unsurprising in another. It was a very unusual election, featuring the first woman to head a major party ticket and a reality TV star/famous guy heading the other major party ticket. A reasonable expectation would have been a larger turnout, maybe not as large as 2008, but a lot larger than it was. The confounding factor, or course, is the extended (and continuing) effort by one of the major parties to create new standards for voter registration; this effort, it seems to me from these data has worked remarkably well. Voter turnout simply at the 2012 level would have meant roughly 9 million additional voted cast this year. As it was, the total number of voted declined from about 129 million to about 125.5 million, instead of rising by al all, even though the population of eligible voters rose by about 10 million.
If my suggestion that the decline in voting was in large part caused by restrictions on registration, then we have, I think, even more reason for concern.