Determining the true level of voter participation in Shelby County is like trying to come up with a single reason for low voter turnout: It’s complicated.

Voter turnout in the March 8 schools consolidation referendum citywide was 17 percent of the 420,000 registered city voters.

For years, election officials – Democrat and Republican – have acknowledged voter rolls in Shelby County include a varying number of voters who have either moved away or died without the rolls being purged.

Between now and the Arlington and Lakeland elections of Sept. 15, the Shelby County Election Commission plans to purge voters who have not voted in at least the last two presidential elections.

Elections administrator Richard Holden said the purge should make voter turnout percentages a more accurate reflection of voter turnout. But how far off the mark the percentages are now is a guess.

“When the hue and cry occurs … it’s folks that haven’t participated in eight to 10 years after registering,” Holden said. “It’s not like anybody’s ox is being gored.”

Holden said the county has more than 66,000 “inactive” voters – those who have missed two consecutive federal general elections that occur every two years, including congressional mid-term elections.

Inactive voters aren’t barred from voting. But they will be the voters who get a notice from the Election Commission asking them to indicate if they still live at the address on their voter registration forms.

Based on past efforts under federal law to correct addresses, Holden estimated 6,000 may be purged because they’ve moved outside the county and another 2,000 may remain voters but with different addresses where they have moved within Shelby County.

The presidential general elections every four years are the only election cycle that consistently draws more than half of the county’s voters to the polls.

Since 1968, voter turnout for the presidential general election has ranged from a low of 57 percent in 2004 to 74 percent in 1980.

Exclude that election cycle and it has been 16 years since more than half of the county’s voters showed up for any other election.

The November general elections of 1994 drew 56.7 percent of the county’s 484,514 voters cast ballots. On the ballot were congressional midterm elections and an open race for governor featuring Memphian Don Sundquist as the GOP nominee and winner.

The next highest turnout since 1994 was 41.2 percent in the November 2002 general election. It was another midterm election year with another open race for governor, this time won by Nashville Democrat Phil Bredesen.

Holden said this month’s 17 percent showing is about what he expected given its status as a special election.

Shelby County Commissioner Steve Mulroy, a law professor at the Cecil C. Humphreys School of Law at the University of Memphis and a former Justice Department attorney who worked in voting rights cases, agrees.

“Seventeen percent turnout on a dreary day on an issue that was very confusing to many voters is not necessarily all that low,” he said although he described the 2-1 margin of victory for the consolidation measure a mandate.

“You have to look at the margin of victory,” Mulroy said. “And if you’ve got a margin of victory of two to one, it seems to me that ends the inquiry right there.”

There hasn’t been a purge locally because of the busy election schedule. It’s been a decade since Shelby County voters had an off election year and the next one is 2013. Democrats in other Tennessee counties complained that several of the early county purge attempts since 2008 were attempts to purge voters who had left unanswered questions on voter registration forms.

“What you’re supposed to do is identify only those voters who have failed to vote in the last two presidential elections and then send them a notice to their registration address and give them a certain amount of time to respond,” Mulroy said, matching Holden’s description of how the upcoming process will work in Shelby County.

“To my knowledge that doesn’t allow you to go through the files and send notices to purge people who simply have failed to fill out the forms correctly,” Mulroy said.