With 16 candidates on the ballot in this year’s mayoral election, it can be hard to pick one candidate, let alone three.

San Francisco is asking voters to do just that in this year’s mayoral election with an alternative system called ranked-choice voting. The system has only been used once in the city, for the mayor’s race in 2007 when Gavin Newsom won with 70 percent of first choice votes.

Ranked-choice voting, also known as instant runoff voting, allows voters to list up to three candidates as their choice for the position instead of the traditional one choice. In San Francisco the voter may list only one candidate, known as bullet voting, or two candidates and leave the other columns blank.

But the system is prone to ballot error, especially in an election with many candidates, because not everyone understands how it works.

“In places where the ballots were longer, people make more errors, so the ballot does cause people to make some errors when they’re voting,” said SF State associate professor of political science Francis Neely, who studied ballot images from the first two ranked-choice voting elections in San Francisco in 2004 and 2005.

Toward the beginning of its use, only 54 percent of voters even knew of the new system’s use in elections, according to Neely.

“A bunch of people showed up and all of a sudden found out that in this race for Board of Supervisors that they had to rank the candidates, not just pick one like they usually do,” Neely said. “That’s problematic because ranking candidates takes more information and people should come prepared for that. If you didn’t, you may not know enough about the other candidates to give a good ranking.”

When people don’t know enough about the candidates, they generally don’t fill out the other two options.

“Often it is the case that a sizable number of people don’t rank the candidates, they just pick one,” Neely said. “So it’s not uncommon for a third of the people voting in a system like this to just pick one candidate.”

The intricacies of the system plus the fact that it is not required to select three candidates means that ranked-choice voting can often produce strange results.

“It’s often the case that if you look at the number of votes cast for that office and then you look at the final number that the winner got for all the ranked-choice voting rounds and eliminations that the winner got less than a majority of all the votes cast for that office,” Neely said.

When no candidate has a clear majority in the first round of voting, the candidate with the fewest votes is eliminated and all votes are transferred to the second choice, according to the San Francisco Department of Elections. The counting continues in this cycle of elimination and transfer until one candidate gains a majority.

This system encourages more candidates to stay in the race through elections because eliminations and vote transfers give each one a chance.

“You no longer have to be a viable contender to stay in the race. Because usually you get down to three or four or maybe two or three and you know they’re the most popular, they’re the most likely, and the other ones don’t have a chance to get more votes than them,” said SF State assistant professor of political science Jason McDaniel. “But now these candidates at the bottom of the pile are saying ‘I might get the second and third place votes and so I have no incentive to drop out of the race.’”

This outcome was demonstrated in Oakland just last year when Jean Quan narrowly edged out front-runner Don Perata to become mayor because of the second and third choice votes.

The ranked-choice voting system was passed as an amendment to the San Francisco City Charter in March 2002 by voters to eliminate the need for expensive runoff elections.

Neely admitted that ranked-choice voting is far from perfect, but no system really is.

“There is no election system that produces a consistent, good, undeniable, unambiguous outcome,” he said, adding that the system still allows some voter freedom. “It allows somebody to vote sincerely.”

Some students like the sound of that.

“It sounds a little saner,” said SF State senior Gregory Done. “The regular system isn’t as democratic.”