Republican turnout is up and Democratic turnout is down in the 2016 primary contests so far. That has some Republicans giddy for the fall; here’s an example, from a March 1 Washington Times article:

Republicans continued to shatter turnout records in their presidential primaries and caucuses Tuesday, while Democrats lagged behind in what analysts said was a clear indication of an enthusiasm gap heading into the general election.

And some commentators are saying that Democrats should be nervous. From The Huffington Post, last month:

But Democratic Party elites shouldn’t be high-fiving each other. They should be very, very worried. In primary after primary this cycle, Democratic voters just aren’t showing up.

But Democrats shouldn’t worry. Republicans shouldn’t celebrate. As others have pointed out, voter turnout is an indication of the competitiveness of a primary contest, not of what will happen in the general election. The GOP presidential primary is more competitive than the Democratic race.

Indeed, history suggests that there is no relationship between primary turnout and the general election outcome. You can see this on the most basic level by looking at raw turnout in years in which both parties had competitive primaries. There have been six of those years in the modern era: 1976, 1980, 1988, 1992, 2000 and 2008.

PARTY WITH HIGHER PRIMARY TURNOUT WINS … YEAR DEMOCRATIC REPUBLICAN POPULAR VOTE ELECTORAL COLLEGE 1976 16.1m 10.4m ✓ ✓ 1980 18.7 12.7 1988 23.0 12.2 1992 20.2 12.7 ✓ ✓ 2000 14.0 17.2 ✓ 2008 37.2 20.8 ✓ ✓ Primary turnout isn’t related to the general election outcome Source: Politifact

As first written up by PolitiFact, the party that had higher turnout in the primary won the national popular vote three times and lost three times. If you look at the Electoral College, the party that had the higher turnout in the primary won four times. That can hardly be described as predictive.

Let’s dig a little deeper, though. Voters in many states can participate in a primary only if they are registered members of the party. Democrats usually have a registration advantage over Republicans, so it follows that Democrats usually have higher turnout. Indeed, Democratic turnout exceeded Republican turnout in five of the six primary elections in our data set, including 1980 and 1988; the Democratic candidate lost by more than 7 percentage points in the general election in both of those years. Could it be that what matters is the change in turnout from the last time there was a competitive primary?

PARTY WITH GREATER CHANGE IN PRIMARY TURNOUT … YEAR DEMOCRATIC REPUBLICAN WINS POPULAR VOTE WINS ELECTORAL COLLEGE 1980 +2.7m +2.3m 1988 +4.2 -0.5 1992 -2.7 +0.5 2000 -6.2 +4.5 ✓ 2008 +23.2 +3.6 ✓ ✓ The change in turnout doesn’t predict the general election either … Source: Politifact

Looking at the change in the number of votes, we see the opposite of what we might expect. In four of five elections in our data set, the party with the larger raw vote increase in the primary lost the national popular vote in the fall. For the Electoral College, the party with the larger vote increase lost three of five times.

Finally, we can look at the percentage change in primary turnout. It’s easier for the party that has a higher base of registered voters to have a greater increase (or decrease) in raw vote turnout. Percentage change helps control for that.

PARTY WITH GREATER % CHANGE IN PRIMARY TURNOUT WINS … YEAR DEMOCRATIC REPUBLICAN POPULAR VOTE ELECTORAL COLLEGE 1980 +17% +22% ✓ ✓ 1988 +22 -4 1992 -12 +4 2000 -31 +35 ✓ 2008 +165 +22 ✓ ✓ … neither does the percentage change in primary turnout Source: Politifact

Here we see the same story. The party whose primary turnout improved the most won the national popular vote in the general election two of five times and won the Electoral College three of five times. In 2000, Democrats saw a large decrease in primary turnout, while Republicans saw a large increase. That fall, we had one of the closest elections ever.

You might have noticed in the tables above that the Democrats in 2008 had the largest turnout and the largest increase in turnout. I suspect that many of the commentators who think the Republican candidate in the fall will benefit from higher turnout in the Republican primaries are remembering how Barack Obama easily won the general election in 2008. It turns out, however, that this pattern doesn’t hold when we look back in time.

Still, the 2008 campaign is instructive in another way. Democratic primary turnout was high because it was a very competitive contest. People turn out to vote when they think their vote may make a difference. Let’s re-examine the raw turnout for each party and the popular vote margin by which the nominee beat the runner-up in the primary.

NOMINEE’S WINNING MARGIN IN PRIMARY PRIMARY TURNOUT YEAR DEMOCRATIC REPUBLICAN DEMOCRATIC REPUBLICAN D-R DIFF. 1988 +13 +49 23m 12m +11m 2008 -1 +26 37 21 +16 1980 +14 +36 19 13 +6 1992 +32 +50 20 13 +8 1976 +20 +7 16 10 +6 2000 +54 +28 14 17 -3 Competitive presidential primaries lead to higher turnout Source: Dave Leip, Politifact, Wikipedia

In five of the six years in our data set, the party that had a smaller vote share margin between its nominee and runner-up — that is, the one with the more competitive contest — had higher turnout. Indeed, the difference in margin for the two winners and the difference in raw turnout for each party had a fairly high correlation of -0.81. The only year in which turnout was higher in the less competitive primary was in 1976, when Jimmy Carter won just 40 percent of the primary vote and had serious competitors until the end of the primary calendar. Both sides were quite competitive that year.

So it shouldn’t be surprising that Republican turnout is higher than Democratic turnout this year. Hillary Clinton is a commanding front-runner on the Democratic side, while the front-runner on the Republican side has earned only one-third of the vote and less than half the delegates allocated so far. Voters are turning out for the more competitive contest.