An Analysis of Key Numbers in the NFL

The concept of "Key Numbers" in betting on pro football is nothing new. Ask anyone familiar with the sport and they will likely know that the most common final result of an NFL game is a three point margin. Often a tied game is decided in the final minute with a game winning field goal. Or a game that goes into Overtime is much more likely to be decided by a field goal than by a touchdown.

How frequent does that three point margin occur? Between 1981 and 1998 there have been 3,942 regular season games played by non-Replacement players (during the 1987 Players' strike the NFL did play three weeks of games with mostly non-roster players). Of those nearly 4,000 games over 15% of them, 597, have been decided by exactly three points. That's more than twice the number of games decided by the next most common number. 280 games, or just over 7%, have been decided by exactly 7 points. In fact, the ten most frequent numbers account for over 60% of all final margins of victory. Here is a list of the NFL's Top Ten Victory Margins:

Margin Occurrences Percentage Cumulative %
3 597 15.1% 15.1%
7 280 7.1% 22.2%
6 237 6.0% 28.2%
10 233 5.9% 34.1%
4 230 5.8% 39.9%
14 191 4.9% 44.8%
1 173 4.4% 49.2%
2 159 4.0% 53.2%
17 148 3.8% 57.0%
11 147 3.7% 60.7%

This information, while interesting, can also be useful to the handicapper and bettor but not in the same form. The above numbers reflect the final margins but handicappers and bettors need to know the answers to a couple of very important questions. First, how often do the FAVORITES win by those margins and, second and more importantly, when favorites win by those exact margins, how often is the pointspread within a half point of those key numbers?

Let's use a simple example to illustrate these questions. We know that 597 times since 1981, the winning margin was exactly three points. Of those 597 games, how often was the winner of the game the pointspread favorite? And more importantly, when the favored team won by exactly 3 points, in how many of those games was that team favored by 2 ½, 3 or 3 ½ points? Do you see where we are headed?

As handicappers we look to find games that present the best opportunities for success in covering the pointspread. Whether we use statistical analysis, situational evaluations, trends, emotions, coaching, historical rivalries or any other factors we deem important in the selection of which games to play, we ultimately select those games that we believe have the highest probability of covering the number.

As bettors we are faced with a different decision-making process. Once we have decided on the teams we wish to play, we now must find the most favorable price. Shopping around for the best line is perhaps even more important than the team we decide to play. Look back upon your experiences over the years and you will recall on more than just a few occasions the number of times you lost a game by that smallest of margins, a half point. Or the number of times you've said to yourself "Boy, am I glad I got that extra half point. It turned a push into a winner (or a loser into a push).

The point here is (pardon the pun) that selecting the likely pointspread winner in a game is only one phase of the process. Getting the best price is just as, if not more, important.

Here in Las Vegas it is not unusual to see lines on the same game fluctuate by as much as a point or a point and a half on many college games, and often there are half point fluctuations on several pro games. Unfortunately as the Sports Book and Casino industries consolidate, there are a fewer number of unaffiliated betting lines available. But there are enough so that at any given time different numbers are available on the same game.

Fortunately, other options are available and one option often misunderstood is the option to 'buy' an extra half point on a game, laying an extra 10% vigorish for the privilege. In other words, instead of laying 11 to 10 on a team at - 6 ½, you have the option to lay 12 to 10 (6-5) and 'buy' that line down from - 6 ½ to - 6. Underdog player have the option to buy the line up to + 7. The question we wish to explore is whether buying that extra half point is a good option and, if so, under what conditions. This is where the 'key number' information presented earlier comes into play.

We saw that there are just ten numbers that account for over 60% of all final margins. One could easily conclude that whenever we have the opportunity to but an extra half point onto or off of one of those 'key' numbers that it should be done. That is not necessarily so. Looking at the frequency, for example, with which the number '3' falls, it is easy to be impressed with the fact that almost one game in seven, 15%, lands on that number. But the questions raised earlier was, 'How often does the FAVORITE win by exactly 3 points?' But even that is not the proper question to ask in determining whether to buy that additional half point. The correct question is "How often does a favorite of 2 ½, 3 or 3 ½ points win the game by exactly 3 points?" In that way we can determine whether or not buying the extra half point onto or off of the number 3 makes sense. Similar questions must be asked about those other 'key numbers' as well.

Here's what we mean. The only time that the key number of 3 is of interest to us is when buying an extra half point enables us to turn a loss into a push or a push into a win. If a 3 point favorite wins by 7 points it is of no consequence to us. The additional half point did not come into play. Whether you laid -3 or bought the half point to lay - 2 ½ did not matter -- you won anyway. Similarly if you played the underdog and bought the half point from + 3 to + 3 ½ you lost anyway when the Favorite won by 7 points. But therein lies the key to the proper analysis of this issue.

How often does a half point matter overall? Let's answer the question this way. Since 1980 there have been 90 games that ended in pushes and another 145 games that fell a half point away from the pointspread. That represents 5.6% of all games played during the past 19 seasons. Obviously many pointspread numbers are involved in that 5.6%, not just the key numbers. But let's delve a little further into this issue and look at how often that extra half point has mattered at various pointspread levels..

Here are some statistics that better allow us to determine whether or not we should buy that half point. The data is from the over 3700 games played between 1982 and 1998 and is reliable. The lines used in the following chart are the Closing Lines from the Stardust Race & Sports Book in Las Vegas.


Based on 1982-1998 Data from 3338 of 3718 Games (89.8% of all Games)


# ofBUYStill ALoss toPush toStillAddedLossesAddedNet
LINETimesTOLossPushWinA WinLossesAvoidedWinningsResult


# ofBUYStill ALoss toPush toStillAddedLossesAddedNet
LINETimesTOLossPushWinA WinLossesAvoidedWinningsResult

This chart reveals some very interesting and useful information. First, here's how to read the chart, which is divided into two parts. The first part of the chart looks at buying a half point from the perspective of a Favorite. Let's use the case of a 6 point Favorite. The chart shows that there have been 180 times when the Closing Line was 6. A Favorite bettor wants to see what happens if he had bought a half point and laid - 5 ½ instead of - 6. The results of those 180 instances are as follows. The 6 point Favorite won by 5 points or less, or lost outright, 82 times, thus still resulting in a losing wager in which the half point did not matter (the 'Still A Loss' column). The 6 point Favorite won by more than 6 points 93 times ('Still A Win" column), again not impacting the pointspread result from having bought the half point. Since the move from - 6 to - 5 ½ cannot result in a 'push' the "Loss to Push" column is zero. However, there were 5 instances in which the 6 point Favorite won by exactly 6 points, thereby making the decision to buy the half point from - 6 to - 5 ½ a good one - it turned what would have been a push into a win (the "Push to Win" column).

That's the first part of the analysis. Now we must examine the effect of buying the half point. We shall use a standard wager of laying $110 to win $100. When you buy the half point you lay 6-5, or $120 to win $100. The 'cost' of buying that half point is $10 per wager and obviously will not affect your bottom line on winning wagers but will increase your losses on wagers you lose. In our example of the 6 point Favorite we see that of the 180 times the line was -6, the Favorite won by more than 6 points 93 times which results in no impact. We'd lay the 6-5 and have it returned to us with our winning in those 93 instances. However, there were 82 instances in which the wager lost at both -6 and - 5 ½, costing us an additional $820 by laying the added vigorish. On the other hand, there were 5 situations in which a game that otherwise would have been a push was turned into a win by laying just 5 ½, netting us an additional $500. The net effect, however, was that buying the extra half point from - 6 to - 5 ½ resulted in an added loss of $320 (the $820 in added losses less the $500 added winning from the pushes turned winners).

The second half of the chart looks at buying the half point from the perspective of an Underdog player. In this case a line of + 6 would be bought up to a + 6 ½ and a similar analysis has been done.

We've concentrated our analysis on lines ranging from 1 to 10 ½ which includes almost 90% of all games played over the past 17 seasons. Most of the 'Key Numbers' referred to at the start of this article are included in the charts.

Notice that buying from a whole number to a half point number (i.e. from 7 to 6 ½) cannot result in a push so the purchase can only change a push into a win or a loss. Buying from a half point number onto a whole number (i.e. from + 4 ½ to + 5) cannot turn what would be a push into a win or a loss but can result in turning a win or a loss into a push.

Now the good news/bad news. The good news is that there are several pointspreads at which buying the extra half point has proven to be profitable over the years, albeit marginally in some cases. Buying Underdogs up from + 2 ½ to + 3, + 3 to + 3 ½ and + 9 ½ to + 10 have all resulted in profits. Likewise, buying Favorites down from - 2 ½ to -2, - 3 to - 2 ½, - 3 ½ to -3 and - 10 ½ to -10 have all resulted in bettering the bottom line.

Unfortunately most Sports Books in Las Vegas do not permit the buying onto or off of a '3'. The Books know the importance of this very key number and realize the potential for both Favorite and Underdog players to profit from this number. If you can find a place that will permit you to buy from - 3 to - 2 ½ or from - 3 ½ to - 3 you should take advantage. Buying from + 2 ½ to + 3 and from + 3 to + 3 ½ is also advised whenever possible. Yet even with the prohibition of buying onto or off of 3 there are still those other instances that have been profitable and are permitted. A secondary source of good news is the revelation that buying a half point in what might seem to be other obvious situations (such as with the numbers 6 or 7) is not justified by historical results and should be avoided even though many people will mistakenly believe that those numbers are just as important as is the number '3'.

By now you can appreciate that picking the pointspread winner of a game is not enough. It is certainly very important but knowing how to play your selection is just as important, especially when the pointspread involves some of the key numbers in the NFL. These opportunities may occur just a few times each season but proper understanding and use of the key number concepts can increase your overall winning percentage and, more importantly, your overall profits.

Good luck during the remainder of the season.

Andrew Iskoe is a writer, researcher, handicapper and lecturer based in Las Vegas. He can be heard regularly on many sports gaming radio shows and has also appeared in a nationally distributed weekly football handicapping television show. Questions or comments may be directed to him at (702) 898-9802 or via e-mail at or on the World Wide Web at

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