NOTE: Since the NFL added a 17th regular season game for the 2021 season, we’ve adjusted all metric totals involving the 2021 season down to a 16-game total.
For years, the NFL key numbers 3 and 7 get sacred treatment from bettors. And while they remain essential spread-betting numbers, they aren’t as important as they used to be.
Key numbers at a glance
• Teams have since attempted and made fewer extra points
• Margin frequencies (especially around key numbers) have changed as a result
Ahead of the 2015 season, the NFL moved the extra point back from the two-yard line to the 15-yard line, effectively making the extra-point attempt go from a 20-yard try to a 33-yard one. The move came on the heels of five straight seasons of 99%-plus success rates and a stretch spanning from 1988, during which the extra-point conversion rate never dipped below 97%.
The change led many savvy bettors to believe that the previous rigidity of NFL’s key numbers would budge as more extra-point attempts would miss and more teams would be inclined to go for two.
With seven seasons of data under our belt since the change, let’s see if the theory held and what kind of effect (if any) it had on key numbers. We’ll look at the seven seasons since the change vs. the seven seasons before the transition to keep sample sizes equal for this examination.
Extra-point attempts and success rate
So first off, did the change lead to a decrease in conversion rate? Extra points converted at a 99.3% rate in the seven years before the shift. In the seven seasons since the change, extra point attempts have dipped to a 93.8% conversion rate - a 5.5% difference.
Across those two timeframes, there was an average of 4.75 extra-point attempts in each NFL game. The dip in conversion rate across those two timeframes means that the expected points from extra-point attempts in an NFL game have dropped from 4.72 to 4.46. That 0.26-point dip in scoring just from extra-point attempts may not seem like much at first, but the impact is easier to contextualize when comparing that dip to the juice you pay to buy a half point.
So if extra-point attempts are more difficult, teams should be discouraged from attempting them as often, right? Let’s take a look.
- In the seven seasons before the change (2008-2014), teams averaged 2.39 extra-point attempts per game
- In the seven seasons following the change (2015-2021), teams have averaged 2.37 attempts per game
- In 2020, teams set the record for most extra-point attempts in league history (1338)
So what gives?
Many NFL fans and bettors know there has been a recent offensive boom. With more touchdowns, teams naturally have more opportunities to kick the extra point. Therefore we should be looking at the rate at which teams opt to kick the extra point compared to going for two.
From 2008 to 2014, teams opted to kick the extra point following 95.1% of touchdowns. From 2015 to 2021, they opted to kick just 90.9% of the time. In 2021 alone, the attempt rate dipped to 88.3%, an all-time low.
Margin of victory in the NFL since 2015
So now we know that:
- Teams are choosing to kick the extra point with less frequency.
- They are kicking them with less success.
So if the previously “perfect” seven-point touchdowns of the past are less likely to happen, are we seeing the distribution of winning margins change? Since the rule change, we’ve seen a collective 2.63% increase in six- and eight-point games.
Although that might seem small within the context of the 5.50% decrease in extra-point success rate, you have to keep in mind that missed extra points aren’t ultimately final as teams have the rest of the game to try and make up for it with two-point attempts.
With that in mind, it intuitively makes sense for the six- and eight-point frequency increase (2.63%) to be slightly less than half the extra-point success decrease (5.50%) as two-point attempts convert at about that rate.
There is noticeably one unexpected increase in margin frequency: five-point games (+1.11%). There aren’t any immediate reasons strictly related to extra-point frequency due to the rule change that could explain the trend. It would be easy to mark it as just a sample size issue for 2015-2021.
But one logical explanation could be the increased availability and usage of data-driven insight on when it is logical to go for two and when it’s not. And the proliferation of that information makes it easy for beat writers, analysts, and fans to bombard coaches with criticism when they bungle those opportunities.
Regarding five-point games: A team leading by five after a touchdown improves its win probability by 3.1% by kicking an extra point and making it a six-point game versus improving its win probability by 5.2% by successfully converting a two-point conversion and making it a full touchdown game. Conversely, a team down five after scoring a touchdown improves its win probability by 2.9% when adding an extra point and making it a four-point game versus 5.0% when converting a two-point try and making it a field-goal game (probabilities via FiveThirtyEight).
Those two situations make up the third- and fourth-largest improvements in win probability when converting a two-point conversion instead of an extra point. This manifests in the (relatively) significant jump in five-point margins. It is the only instance in which it is significantly beneficial to attempt a two-point conversion when trailing and leading by the same number.
Interesting five-point tangents aside, what are the essential takeaways for NFL key numbers for spreads in 2021?
Ultimately three and seven are still king, and 10 and 14 also matter when looking at the (more infrequent) larger point spreads.
Outside of that, 6 and 8 (especially 6) are just a little easier to swallow if the alternative is paying large juice on a seven.
NFL totals since 2015
In the last 20 seasons, the average total has gone from 39.9 to last year’s 46.5 (and notably 2020’s all-time high of 49.6). Despite rapidly increasing NFL totals, average points per game scored have outpaced totals in 16 of the 20 seasons and have done so by an average of 0.95 points in those seasons.
Despite 2020’s 49.6 average points per game being four points higher than 2019’s average and an entire field goal more than the previous all-time high, 2021 reversed course. The 46.0 points scored on average in 2021 not only paced below the average total of 46.5; it was just the third time since 2000 that average points paced below the average total by more than half a point. And all three of those instances have occurred in the last eight seasons, so be wary of inflated overs.
So how has this affected key numbers in totals, if at all? It’s a tricky question, as “key numbers” in totals are nowhere near as rigid or frequent as they are in spreads.
For example, the key number of 3 in spreads occurs in around 15% of all games and 7 in about 9%. In comparison, the most frequent total numbers appear about 4% of the time. Because the peak frequency of key numbers in totals is so low, the relative gaps between those frequencies and the least frequent numbers are not as significant.
For example, the key number of 3 in spreads occurs about 10% more frequently than the least frequent one-score margins, and 7 is a still-respectable 5% more frequently than those numbers. The most frequent key numbers in totals only happen around 3% more often than the less frequent numbers, illustrated below.
As you can see, the “key numbers” in totals are primarily “key ranges.” You can see this with 36-37, 40-41, 43-44, 51 (the lone wolf), 54-55, and 57-58. With the recent boom in scoring, you can see in the far right column that this has shifted scoring frequencies towards higher numbers.
So when it comes to totals, the key takeaway is that although there are certainly more frequented totals in the form of some “key ranges,” they aren’t as firm as key numbers in spreads.
However, it is always advantageous to still play the probabilities, meaning you’d prefer to be above these ranges when playing the Under. When playing the Over, you’d like to be below them. On top of that, there are other game elements to consider when playing totals, such as the weather.
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NFL key numbers FAQs
Key numbers in NFL betting revolve around the most frequent deciding margins in games. Three and seven are the most frequent of all due to the rigid scoring system of the NFL.
Because of how points are scored in the NFL, bettors can use this knowledge to predict the margins in football games.
Despite rule changes in the NFL, traditional key numbers are still by far the most dominant in NFL margins.