Rival fans have long believed that North Carolina and Duke receive favorable treatment from officials. But do they?

Since the 2000-01 season, UNC and Duke have consistently led the ACC, or been among the conference leaders, in both foul disparity and free throw disparity. Which means that UNC and Duke have committed fewer fouls than their opponents, and attempted more free throws than their opponents.

That’s not a surprise. Both the Tar Heels and Blue Devils have won two national championships each since 2000. They’ve had some of the ACC’s best teams – and some of its most difficult-to-defend players – and when they lead close games late, opposing teams have to foul and hope they miss free throws.

Given Roy Williams’ preference for more fluidity in college basketball, perhaps it’s not a surprise, either, that for years his teams at UNC have been among the ACC’s leaders in fewest fouls committed. In each of the past six seasons the Tar Heels, not known for utilizing a pressuring, overly aggressive defense, have ranked among the top three in the ACC in fewest fouls committed per game in conference play.

During the same time, Duke, known for its aggressive, overplaying defense, never ranked among the top three in fewest fouls committed. In fact, it was more the opposite. Duke is called for a lot of fouls, relative to the competition. The Blue Devils since the 2000-01 season rank seventh in the ACC in fouls committed per game.

Entering the ACC tournament, Duke in conference games had committed an average of 18.3 fouls per game – fourth-most in the league behind Virginia Tech, Maryland and Wake Forest. Historically, though, Duke has done the best job of any team in the ACC when it comes to drawing fouls. Since the 2000-01 season, Duke in ACC games has drawn an average of 20.5 fouls per game – most in the league.

Wake Forest, which has drawn an average of 20.1 fouls per game in conference games since 2000-01, ranks second. UNC (19.7) is third, with Maryland (19.1) and N.C. State (19.1) right behind.

Chris Collins, the Blue Devils’ assistant coach who during the mid-1990s played at Duke, said accusations of officiating bias are part of “the nature of cheering for sports teams.” Not that he pays much attention to it.

“I think with the advances in technology and with social media and with all the different coverages, with print and broadcast media, I think it heightened the awareness of all that stuff,” he said.

The foul data confirms, in general, that good teams draw more fouls and commit fewer, and that mediocre and bad ones draw fewer fouls and commit more. Three of the ACC’s five national championship teams since the 2000-01 season – UNC in 2009, Maryland in ’02 and Duke in ‘01 – all led the ACC in fouls drawn per game in conference play. The league’s other two national title teams – Duke in 2010 and UNC in 2005 – ranked among the top four.

Since the 2000-01 season, UNC and Duke rank first and second in the ACC in foul disparity – the number of fouls each team has committed each game, compared to the number it has drawn each game – and free throw disparity. During the past 13 seasons, UNC on average has attempted 78.3 more free throws per season than its opponents in ACC games. Duke has shot an average of 57.6 more free throws per season than its opponents in ACC games.

Under Williams, UNC has been one of the best teams in the country at getting to the foul line – in part because UNC usually has utilized an inside-out offensive philosophy that generates fouls in the post.

The Tar Heels have had more difficulty this season getting to the free throw line because they have been more perimeter oriented. Entering the ACC tournament, the Tar Heels ranked 245th nationally in free throw attempts, but they’d also allowed opponents the 22nd-fewest attempts in the nation.

“Pace of the game is always one of the reasons, number of possessions,” Williams said, explaining his team’s lack of free throw attempts. “When you’re playing somebody that wants to go slower, you’re not going to have as many possessions. So that’s the first one.

“But the second one is how aggressive are we. And you can be aggressive two ways – taking a quick 3 with a good shooter. And that still may be OK. Or attacking the basket. And I’ve always liked to attack the basket, either by dribble or pass.”

UNC, which lacks a reliable offensive post presence, hasn’t been able to attack the basket as much as Williams would like. And driving lanes began to appear only after UNC began to spread the floor with a four-guard starting lineup.

Carter: 919-829-8944 Twitter: @_andrewcarter