The Seattle Seahawks allowed just 277 points (17.3) during the 2015 regular season, thus becoming the first team since the 1970 AFL-NFL merger to lead the league in scoring defense in four consecutive seasons, per Elias Sports Bureau (via ESPN Stats & Info).
Unlike in 2012 and 2014, when the Seahawks led by at least 27 points, the scoring defense title came down to the wire in 2015, with the Cincinnati Bengals (279 points) finishing just two points behind Seattle. The Kansas City Chiefs (287 points) and Denver Broncos (296 points) were also within striking distance.