In 2018, Clemson recorded the first 15-0 national championship season in the five-year history of the College Football Playoff. But the Tigers achieved that perfect record without perfect attendance.

Clemson did not sell out a single home game during the 2018 season, including the rivalry game against South Carolina. It was the first season in which Clemson did not notch at least one sellout since 2009, Dabo Swinney’s first full year as head coach.

Clemson reported an average crowd of 80,400 fans, filling Memorial Stadium to 98.7 percent of its capacity. The South Carolina crowd of 81,436 was Clemson’s largest of the year, but it was only the third time the rivalry has attracted fewer than 82,000 to Death Valley since 1982. The other instances were in 2010 and 2016.

Clemson ranked 12th in the Division I bowl subdivision in average stadium capacity. Merely five teams averaged a sellout— Oklahoma, Michigan, Nebraska, Georgia and Utah. Clemson also trailed its powerhouse peers Alabama, Ohio State and Penn State in that category. But also Central Florida, Kansas State and North Carolina State.

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The odd mixture of schools at the top of the ledger reveals the inexact science behind ticket sales. The conventional culprits of expensive ticket costs, low demand and enhanced television viewing experiences are not the only reasons for the empty seats.

“Our biggest factor tends to be the opponent and how many folks they bring,” said Clemson assistant athletic director for ticket operations Owen Godfrey, alluding to the tickets Clemson allots to opponents.

The highest allotment figure is for South Carolina, biennially Clemson’s most attractive ticket. Last season, Clemson allotted 8,000 tickets to South Carolina. In accordance with a league-wide agreement, visiting Atlantic Coast Conference schools can request a maximum of 4,300 tickets.

The allotment for all other visitors was stipulated in their respective contracts. However, outside of Carolina, few of Clemson's opponents guaranteed more than 1,000 tickets. Clemson recouped the unused tickets in late April, but it could not package them into a full season-ticket deal without the marquee Carolina game.

“We sold as many season tickets down to that guaranteed number at 8,000,” Godfrey said. “When we do that, we turn away some folks that want to buy full season tickets, because, when the schedule doesn't include South Carolina, or if we did it this year and it didn't include Texas A&M, it's a challenge.”

Clemson advertises remaining season ticket package deals each June. In July, Clemson posts the unused tickets for single-game sales. According to Godfrey, fans searching for single-game seats are conditioned to shop the secondary marketplaces, like StubHub and SeatGeek, so they often bypass the Clemson ticket office.

“Our toughest chore here is just building awareness that we actually have those tickets,” Godfrey said. “If you hear that we're sold out of season tickets, you don't know you can order directly from Clemson.”

The demand for smaller packages and single-game tickets was low last season. The season opener against Furman attracted more fans (80,048) than the matchup with ACC foe Louisville (78,741).

During its previous undefeated regular season, in 2015, Clemson hosted marquee matchups against Notre Dame and Florida State. Clemson had an easier time selling three, four and five-game packages that included Appalachian State, Georgia Tech and Wake Forest.

Clemson sold out every game that season. Its only sellouts since then were dates with Louisville, North Carolina State and South Carolina in 2016 and Auburn in 2017.

The highest allotment for the 2019 season, 5,000 tickets, is for Texas A&M, the anchor of the schedule. Traditional season ticket packages are renewable. Although Clemson has 3,000 more seats to sell this season than last year, it cannot exceed the South Carolina allotment for 2020.

Clemson and South Carolina agreed to decrease that allotment to 7,000. According to Godfrey, Clemson has sold 400 of those additional 1,000 season tickets.