Democrats went into Election Day with confidence. Hillary Clinton was leading in the polls, and early voting seemed to indicate that her supporters had enough enthusiasm to ensure victory. More than 46 million people voted early in 2016, a very slight increase over turnout in 2012, and turnout was high among women and Latinos (though there was a worrying decrease in black early voter turnout).

Then she lost.

The polls, as we know, ended up drastically underestimating Donald Trump’s support, and whatever advantages Clinton had in early voting proved insufficient. Among the battleground states, she lost Florida, North Carolina, Michigan, Wisconsin, and Pennsylvania.

The problem, as I reported previously, is that it’s tough to draw conclusions about the final election result from early voting numbers. Different states have different early voting laws and report ballot returns inconsistently, and assumptions based on party affiliation are fallible at best.

“Clinton banked a lot of early votes, but there just weren’t enough left on Election Day,” says Paul Gronke, a political scientist with Reed College and the director of the Early Voting Information Center.

Early voting is a measure of enthusiasm — not an indicator of overall turnout

Early voting is usually a good measure of enthusiasm; lots of early voters means lots of decided voters. It can also help campaigns figure out where to focus their get-out-the-vote resources on Election Day.

But early voting totals aren’t necessarily an indicator of overall turnout — they might just shift when voters vote rather than increase the total number of voters. And early voting can’t always indicate whether or not a campaign's mobilization efforts have tapped out. Think of it like a pie, Gronke says: “If you cut out a few slices with early voting, it doesn’t mean the pie has somehow changed in size.” Just because more Latinos are turning out early for Clinton doesn’t mean there are more Latino voters overall.

From the numbers this year, we can see voters do like early voting reforms: There are long lines at the polls on Election Day, and early voting expands voters’ options, especially when it comes to missing work or school. But it’s still up for debate whether it is an effective way to boost overall turnout. For now, there are too few elections with robust early voting opportunities, and too few studies correlating early voting figures with eventual turnout.

Early voting doesn’t always tell us who will win the election

“It is quite difficult to discern what the election results will be from early voting numbers,” University of Wisconsin early voting expert Barry Burden said. “The patterns do not tell a coherent national story. … Ballots are coming in at different rates for the parties in each state. The messages appear to differ from one state to the next.”

There are a lot of limitations: States reporting early voting totals don’t always include all counties; some states, like North Carolina, require party registration, while others, like Wisconsin, don’t; and numbers derived from party registrations are fallible. These distinctions can explain some of the early results.

University of Denver political scientist Seth Masket crunched the numbers for FiveThirtyEight on how well early voting numbers predicted the final tally in past elections. He concluded: “The relationship is positive, but it’s pretty noisy. In other words, knowing how a party is doing in early voting doesn’t tell you much about how it will do once all the votes are counted.”

In fact, he found that looking at early voting numbers in 2012 would give you “wildly misleading” results:

Democrats maintained substantial leads among early voters in North Carolina, Louisiana and West Virginia, and were trailing by a relatively narrow margin in Oklahoma, but still lost those states when all the votes were counted. Republicans won early voters in Pennsylvania and Colorado but lost the final tallies there. Maryland was a safely Democratic state in 2012, but the 75 percent of the early vote that went the Democrats’ way was a far cry from the 63 percent of the total vote they won once voting was finished.

For Clinton, this year, early voting gave false hope for a race that was much tighter than any polls and projections suggested.