For many sports fans, hockey still conjures images of players pummeling each other with fists, fourth-line goons and line brawls. Yet since 2009, the number of fights in the NHL, and the number of fights per game, has been in decline.

How much has it declined? Consider this: According to HockeyFights.com’s decades of data, provided to Yahoo Sports, the 0.28 fights per game average in the NHL’s 2015-16 regular season is the lowest total since the 1967-68 season (0.21). It’s also the first time the NHL’s fights-per-game average came in under 0.30 in 48 years.

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That season had 444 games and 12 teams, while this season had 1,230 games and 30 teams.

The total number of fights in the 2015-16 season – with “fight” defined as “when at least one player involved receives a fighting major” – finished at 344. That’s fewer than we saw in either the 2012-13 (347) or 1994-95 (506) lockout seasons, and the lowest total in the NHL since 1973-74, which had 267 fights.

Here’s a look at the trends:

View photos Graphic by Amber Matsumoto/Yahoo Sports More

What caused fighting reach such historic lows? A few factors:

No Room for One Dimensional Players – The four-minute-a-night fourth-line goon is the dodo bird of the NHL. The game is too fast, the necessity to have every player in the lineup contribute something beyond fists is too great. The players who fight the most today also contribute something beyond their fists: Consider that Derek Dorsett of the Vancouver Canucks, who was second in the NHL with 11 fighting majors this season, also had 16 points in 71 games.

As a result, players are no longer fighting their way into the League like they did in the 1980s and 1990s. Now, it’s about speed and scoring, and even size isn’t at a premium as it once was.

No More Dance Partners – So if fourth-line goons and enforcers are no long on active rosters, the remaining ones have no one left to fight. As then-Coyotes GM Don Maloney said of enforcer Paul Bissonnette in 2012, whose fights had dropped from eight to one from season-to-season: “It's the lack of takers. Paul is not going out there and grab (Detroit Red Wings star) Pavel Datsyuk."

Supplemental Discipline – The NHL’s Department of Player Safety has helped decrease the number of catastrophic hits we see per season, which then typically lead to fights within a game and then in a subsequent “revenge” game. The NHL also has maintained the instigator rule, which penalizes a player who starts a fight, and instituted rules that have dramatically lessoned the “message sending” fights we used to see in the last moments of a blowout loss.

Finally, Concussion Panic – NHL players are now, more than ever before, cognizant of the potential long-term health effects of playing contact sports. NHL players who fight, meanwhile, have seen peers like Derek Boogaard and Steve Montador die tragically and countless others struggle mightily after suffering multiple concussions as players. The specter of CTE haunts them. Perhaps their appetite for fighting has decreases that awareness increased.

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For the NHL, there’s an ongoing debate about fighting, its place in the game and what its decline means for the sport’s popularity. Perhaps it makes hockey more accessible for sports fans who find it repellent. Perhaps the NHL is a little less interesting, and its personalities a little less magnetic, without it, as we argued here.

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