We don't yet have final numbers on how many Americans voted this year, but preliminary figures suggest that turnout is probably down from 2008 - down in percentage terms, and possibly down in absolute terms as well. The population is growing, but the number of voters seems to be shrinking.

I don't see low turnout as quite the crisis others do. I'm not against high turnout. I'm just unpersuaded that the optimal level is 100 percent.

For example, one common argument is that a higher turnout makes the results of an election more legitimate. By this standard, President Barack Obama's victory in 2008 was less legitimate than Richard Nixon's in 1968. According to the compilation by the American Presidency Project at the University of California at Santa Barbara, nearly 58 percent of the voting-age population cast ballots in 2008, whereas four decades earlier, when Nixon was defeating Hubert Humphrey, nearly 61 percent of the voting-age population went to the polls. Following the same logic, Nixon's win was less legitimate than Dwight Eisenhower's in 1952, which saw a turnout of 63.3 percent - the highest in the past 100 years.

Want higher turnout? The highest in U.S. history came in 1876, at 81.8 percent. The truth is, turnout has been falling for decades. That's why it's a mistake to try placing the blame for this year's drop-off on, for example, Hurricane Sandy. In the first place, a storm that hit the Northeast is a very unlikely contributor to estimated declines of 25 percent in Alaska or 19 percent in Arizona.

More to the point, the 2008 turnout to elect the nation's first black president was an unlikely spike in a trend running very much the other way. This year's turnout represents not an outlier in need of explanation but a regression to the mean.

We haven't broken the 60 percent barrier since the 1960s, although we have been above 50 percent in every recent presidential election except 1996. On only two other occasions has turnout fallen below half of the voting-age population: in 1920, when Warren Harding beat James Cox by the largest popular vote margin (26 percentage points) in modern history; and in 1924, when Calvin Coolidge (who succeeded to the presidency when Harding died in office) defeated Democrat John W. Davis (who would later argue the pro-segregation side in Brown v. Board of Education).

Why do we vote in lower numbers? Maybe because the late 1960s were a time of Vietnam, Watergate and political assassinations, a trilogy that ushered in an era of disillusionment that remains with us. Cynicism and doubt were considered almost un-American as recently as the 1950s. Since the 1970s, a reflexive cynicism about political life has been all but fed to children at birth.

The political scientist Francis Fukuyama has argued that we don't vote because the welfare state has made us comfortable. Others blame technology - in particular, the many gadgets that entertain us at home. Political scientists have long believed that unemployment decreases turnout (although some recent research suggests that losing a job within a month of the election makes one more likely to vote).

And we tend to forget how narrow is the political range in U.S. politics. We elevate to Titanic proportions debates over whether to raise or lower tax rates by a few points, or whether universal health insurance should be achieved by government provision or subsidies in the private market.

Those arguments encompass a broad center, not the fringe.

I mention this only because we can easily forget that a citizen can make a perfectly rational decision not to vote. One might not care about the outcome of the issues that fire committed partisans: Supreme Court appointments, for instance. Another might feel insufficiently informed on matters of great complexity: the effect of marginal tax rates on economic growth, say. Others might decide that politics is an ugly distraction from more attractive pursuits. I'm not sure that the brilliant artist who refuses to put down her brush on Election Day is doing a national disservice.

The point is that voting, though an important measure of civic responsibility, is far from the only one. There is no obvious reason that raising the rate of voter turnout is a more laudable goal than raising the rate of charitable giving.

I understand why the parties place such an emphasis on turnout by voters expected to support its candidate. That is a separate matter. Encouraging people to vote because you think it will help your side isn't a particularly admirable way to think about civic responsibility.

I raise this last point for a reason. We have known for some time that turnout is correlated with positive answers to questions such as whether potential voters trust the government to do the right thing most of the time, or whether they feel that people like themselves have much influence over what the government does. Americans in recent decades have ranked low on those scales - that is, by and large we neither trust the government nor believe that we can influence it.

Those who want higher voter turnout might usefully begin by proving rather than asserting that these beliefs are wrong.

Stephen L. Carter is a Bloomberg View columnist and a professor of law at Yale University. He is the author of "The Violence of Peace: America's Wars in the Age of Obama." His most recent novel is "The Impeachment of Abraham Lincoln."

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