The rate at which ballots cast by unaffiliated voters were rejected in Colorado’s June primary elections was 2.4 percent, lower than some forecasts before the election, Secretary of State Wayne Williams said Friday.

Proposition 108, which Colorado voters approved in 2016, allowed the state’s unaffiliated voters for the first time this year to cast ballots in the state’s partisan primaries without declaring for a party ahead of time.

Under the new system, unaffiliated voters who didn’t request a particular party’s ballot in advance were sent both a Republican and a Democratic ballot.

They were allowed to fill out and return only one of the two ballots, however. If they returned both ballots filled out, their vote was disqualified.

And that double-ballot disqualification rate was 2.4 percent, Williams said.

According to new tallies, of the 293,153 ballots submitted by unaffiliated voters, 6,914 contained voted ballots for both Democratic and Republican candidates, so neither ballot counted.

In a statement, Williams noted that forecasts of the rejection rate before Prop 108 passed had ranged as high as 7 percent, based on the previous experience of Washington state with a similar system.

“I am incredibly proud of the efforts by our county clerks and media partners who helped deliver the message to only vote one ballot,” Secretary of State Wayne Williams said. “Our office will be working with the clerks to improve the percentage in our next primary election, in 2020.”

Williams’ office and other groups had worked for months leading up to the election to publicize the new double-ballot system, and explanatory messages were included with the mailed ballots.

Williams spokeswoman Lynn Bartels said that $900,000 – authorized unanimously by the legislature – was spent on the “UChooseCO” promotional campaign explaining the new primary system.

The final 2.4 percent rejection rate was lower than the percentage reported in mid-June, when the reject rate was 3.4 percent statewide, 4.3 percent in Arapahoe County and 7 percent in El Paso County.

As it turned out, as of Friday, El Paso still had a relatively high ballot rejection rate of 4.8 percent, by far the highest of the state’s largest counties.

The rejection rates were 2.6 percent in Denver County, 0.4 percent in Adams County, 2.7 percent in Arapahoe County, 0.9 percent in Boulder County, 1.4 percent in Douglas County, 1.9 percent in Jefferson County, 1.7 percent in Larimer County, 2 percent in Mesa County and 2 percent in Pueblo County, Williams said.

On the other hand, a handful of counties – mostly small ones – had rejection percentages north of 9 percent: Conejos (13.8 percent), Kit Carson (10.9 percent), Crowley (9.9 percent) and Cheyenne and Sedgwick (both 9.2 percent).

Kent Thiry, the DaVita Inc. CEO who backed the pro-Prop 108 campaign, in a comment provided by the Secretary of State’s office, called it an “excellent first election result and (we) look forward to doing even better next time.”

And Kelly Brough – president and CEO of the Denver Metro Chamber of Commerce, which also had backed 108 – said: “We know Coloradans are smart and engaged and these numbers confirm it. It’s exciting to see Colorado’s unaffiliated voters share their voices earlier in the election process. We’re very proud to have played a role in letting Colorado vote.”