The Seattle Seahawks have allowed the fewest points in the N.F.L. in each of the last four seasons. No team during the Super Bowl era has matched that feat — in fact, the only other team to lead the N.F.L. in points allowed for such a stretch was the Cleveland Browns, who did it in five consecutive seasons from 1953 to 1957.
The Seahawks allowed 15.3 points per game in 2012, 14.4 in 2013, 15.9 last season, and then 17.3 points per game this season. Those numbers do not necessarily stand out as historically dominant — the 1977 Falcons allowed 9.2 points per game, the fewest of any team since 1950 — but that ignores the era in which Seattle plays. The modern N.F.L. is one of the most offensive-friendly environments in league history, so comparing Seattle to teams that played in eras in which the rules were more friendly to defenses is not a fair comparison.
In addition, while Seattle has allowed 15.7 points per game over the last four years, only one other team since 2012 has allowed fewer than 20 points a game. That team, the Cincinnati Bengals, at 19.5, has still allowed nearly 4 more points per game than the Seahawks. In other words, what really distinguishes this Seattle team is how far ahead of the rest of the N.F.L. in this statistic it has been.
One way to measure this is by measuring the number of standard deviations from average. Over the last four years, Seattle has allowed 15.73 points a game, relative to the league average of 22.89. The standard deviation in points allowed by the league’s 32 teams over this period has been 2.62 points per game. This means Seattle, which has been over 7 points a game better than average, has been 2.73 standard deviations better than average, a statistic know as a Z-Score.
As it turns out, that makes Seattle the most successful team in preventing points over a four-year run since 1950. From 1985 to 1988, the Bears allowed 14.00 points a game while the league average was 20.98, and the standard deviation among teams was 2.55 points per game. Therefore, Chicago was also 2.73 standard deviations better than average, although the modern Seahawks edge those Bears slightly, 2.735 to 2.732.
The table below shows the top 30 teams in preventing points since 1950, as measured by this metric.