A 20 Year Analysis Of NFL Betting :

Kramer · #1 05-22-2007, 09:19 PM

Season Totals
1. Table 1 shows the average away, home, and combined score by season.
Table 1: Season Totals
Season Away Total Home Total Game Total
1983 20.82 22.91 43.74
1984 19.88 22.37 42.25
1985 19.05 23.65 42.7
1986 19.1 21.86 40.96
1987 20.73 22.7 43.43
1988 18.72 21.65 40.37
1989 18.96 22.41 41.37
1990 18.11 22.12 40.23
1991 17.12 20.79 37.91
1992 17.38 20.22 37.6
1993 17.38 20.5 37.89
1994 19.43 21.23 40.65
1995 20.56 22.82 43.38
1996 18.39 22.55 40.94
1997 19.17 22.09 41.26
1998 19.47 23.19 42.66
1999 19.21 22.48 41.69
2000 18.97 22.12 41.09
2001 19.19 21.36 40.55
2002 20.54 23.03 43.56
2003 19.06 22.65 41.72
Total 19.11 22.14 41.25

One practical piece of information table 1 shows is that on average the home team outscores the visiting team by 3.03 points. So the rule of thumb that home field advantage is worth 3 points is well supported.

Half Time Totals
Table 2-A shows the average total in the first half, second half, and overtime. For betting purposes overtime is part of the second half.
Table 2-A: Half Time Averages by Season
Season Away Half 1 Home Half 1 Total Half 1 Away Half 2 Home Half 2 Total Half 2
1983 9.94 11.59 21.53 10.88 11.33 22.21
1984 10 11.18 21.18 9.88 11.19 21.07
1985 8.91 12.08 20.99 10.14 11.57 21.72
1986 8.96 11.5 20.46 10.14 10.36 20.5
1987 10.33 11.58 21.91 10.4 11.11 21.52
1988 9.47 11.37 20.84 9.25 10.28 19.53
1989 8.84 11.44 20.28 10.12 10.97 21.09
1990 9.08 11.53 20.61 9.03 10.59 19.62
1991 8.27 10.48 18.75 8.85 10.31 19.15
1992 8.05 10.37 18.42 9.32 9.85 19.18
1993 8.84 10.26 19.1 8.55 10.24 18.79
1994 9.68 11.16 20.83 9.75 10.07 19.82
1995 10.54 11.94 22.48 10.02 10.87 20.9
1996 9.13 12.09 21.22 9.26 10.46 19.72
1997 9.39 11.38 20.77 9.78 10.7 20.48
1998 9.67 11.9 21.57 9.8 11.29 21.09
1999 9.48 12.03 21.51 9.73 10.46 20.19
2000 9.33 11.31 20.64 9.64 10.81 20.45
2001 9.48 10.54 20.02 9.72 10.82 20.53
2002 10.02 11.75 21.77 10.52 11.27 21.79
2003 9.64 11.66 21.29 9.43 11 20.42
Total 9.39 11.39 20.78 9.72 10.74 20.47

This chart shows that home field advantage is worth 2.01 points in the first half and only 1.02 in the second half. It also shows the first half outscores the second half by 0.32 points, despite overtime counting towards the second half.

Table 2-B shows a distribution of the total points scored in each half for both teams individually. For this chart overtime is counted in the second half.
Table 2-B: Half Time Totals
Half Time Total Number First Half Number Second Half Number Both Halves Probability First Half Probability Second Half Probability Both Halves
0 1138 1292 2430 11.19% 12.7% 11.94%
1 0 0 0 0% 0% 0%
2 7 20 27 0.07% 0.2% 0.13%
3 1222 918 2140 12.01% 9.02% 10.52%
4 0 0 0 0% 0% 0%
5 23 17 40 0.23% 0.17% 0.2%
6 630 520 1150 6.19% 5.11% 5.65%
7 1520 1735 3255 14.94% 17.06% 16%
8 11 77 88 0.11% 0.76% 0.43%
9 168 242 410 1.65% 2.38% 2.02%
10 1475 1220 2695 14.5% 11.99% 13.25%
11 8 48 56 0.08% 0.47% 0.28%
12 71 90 161 0.7% 0.88% 0.79%
13 562 571 1133 5.52% 5.61% 5.57%
14 1002 1200 2202 9.85% 11.8% 10.82%
15 19 77 96 0.19% 0.76% 0.47%
16 138 184 322 1.36% 1.81% 1.58%
17 756 626 1382 7.43% 6.15% 6.79%
18 12 46 58 0.12% 0.45% 0.29%
19 33 54 87 0.32% 0.53% 0.43%
20 271 247 518 2.66% 2.43% 2.55%
21 405 429 834 3.98% 4.22% 4.1%
22 15 32 47 0.15% 0.31% 0.23%
23 53 58 111 0.52% 0.57% 0.55%
24 267 199 466 2.62% 1.96% 2.29%
25 7 14 21 0.07% 0.14% 0.1%
26 13 16 29 0.13% 0.16% 0.14%
27 79 50 129 0.78% 0.49% 0.63%
28 133 114 247 1.31% 1.12% 1.21%
29 4 7 11 0.04% 0.07% 0.05%
30 20 8 28 0.2% 0.08% 0.14%
31 55 29 84 0.54% 0.29% 0.41%
32 0 5 5 0% 0.05% 0.02%
33 4 1 5 0.04% 0.01% 0.02%
34 10 3 13 0.1% 0.03% 0.06%
35 23 12 35 0.23% 0.12% 0.17%
36 1 4 5 0.01% 0.04% 0.02%
37 1 2 3 0.01% 0.02% 0.01%
38 6 4 10 0.06% 0.04% 0.05%
39 0 0 0 0% 0% 0%
40 0 0 0 0% 0% 0%
41 4 1 5 0.04% 0.01% 0.02%
42 2 0 2 0.02% 0% 0.01%
43 0 0 0 0% 0% 0%
44 0 0 0 0% 0% 0%
45 3 0 3 0.03% 0% 0.01%
46 0 0 0 0% 0% 0%
47 0 0 0 0% 0% 0%
48 0 0 0 0% 0% 0%
49 1 0 1 0.01% 0% 0%
50 0 0 0 0% 0% 0%
51 0 0 0 0% 0% 0%
52 0 0 0 0% 0% 0%
Total 10172 10172 20344 100% 100% 100%

Quarter Time Totals
Table 2-C shows a distribution of the total points scored in each quarter for both teams individually. Overtime is not counted towards any quarter.
Table 2-C: Quarter Time Totals
Quarter Time Total Number Quarter 1 Number Quarter 2 Number Quarter 3 Number Quarter 4 Number All Quarters Probability Quarter 1 Probability Quarter 2 Probability Quarter 3 Probability Quarter 4 Probability All Quarters
0 4342 2545 4084 3074 14045 42.69% 25.02% 40.15% 30.22% 34.52%
1 0 0 0 0 0 0% 0% 0% 0% 0%
2 29 13 23 45 110 0.29% 0.13% 0.23% 0.44% 0.27%
3 1766 1836 1633 1370 6605 17.36% 18.05% 16.05% 13.47% 16.23%
4 0 0 0 0 0 0% 0% 0% 0% 0%
5 11 18 7 17 53 0.11% 0.18% 0.07% 0.17% 0.13%
6 222 507 297 492 1518 2.18% 4.98% 2.92% 4.84% 3.73%
7 2457 2192 2550 2604 9603 24.15% 21.55% 25.07% 25.6% 24.09%
8 1 15 61 127 204 0.01% 0.15% 0.6% 1.25% 0.5%
9 42 105 61 116 324 0.41% 1.03% 0.6% 1.14% 0.8%
10 547 1165 557 864 3133 5.38% 11.45% 5.48% 8.49% 7.7%
11 3 16 24 38 81 0.03% 0.16% 0.24% 0.37% 0.2%
12 5 29 10 38 82 0.05% 0.29% 0.1% 0.37% 0.2%
13 50 253 78 186 567 0.49% 2.49% 0.77% 1.83% 1.39%
14 535 835 568 768 2706 5.26% 8.21% 5.58% 7.55% 6.65%
15 2 6 24 39 71 0.02% 0.06% 0.24% 0.38% 0.17%
16 8 36 13 31 88 0.08% 0.35% 0.13% 0.3% 0.22%
17 76 301 82 170 629 0.75% 2.96% 0.81% 1.67% 1.55%
18 0 4 3 7 14 0% 0.04% 0.03% 0.07% 0.03%
19 0 6 3 4 13 0% 0.06% 0.03% 0.04% 0.03%
20 6 46 11 22 85 0.06% 0.45% 0.11% 0.22% 0.21%
21 62 174 69 124 429 0.61% 1.71% 0.68% 1.22% 1.05%
22 1 4 2 7 14 0.01% 0.04% 0.02% 0.07% 0.03%
23 0 6 1 3 10 0% 0.06% 0.01% 0.03% 0.02%
24 3 26 6 13 48 0.03% 0.26% 0.06% 0.13% 0.12%
25 0 0 1 1 2 0% 0% 0.01% 0.01% 0%
26 0 1 0 1 2 0% 0.01% 0% 0.01% 0%
27 0 2 0 0 2 0% 0.02% 0% 0% 0%
28 4 22 4 10 40 0.04% 0.22% 0.04% 0.1% 0.1%
29 0 0 0 0 0 0% 0% 0% 0% 0%
30 0 1 0 1 2 0% 0.01% 0% 0.01% 0%
31 0 6 0 0 6 0% 0.06% 0% 0% 0.01%
32 0 0 0 0 0 0% 0% 0% 0% 0%
33 0 1 0 0 1 0% 0.01% 0% 0% 0%
34 0 0 0 0 0 0% 0% 0% 0% 0%
35 0 1 0 0 1 0% 0.01% 0% 0% 0%
10172 10172 10172 10172 40688 100% 100% 100% 100% 100%

Following are the average points scored by each team by quarter:
Quarter 1: 4.04
Quarter 2: 6.35
Quarter 3: 4.39
Quarter 4: 5.73

Margin of Victory
Table 3 shows the distribution of the margin of victory over all games from 1983 to 2003, except Super Bowls.
Table 3: Margin of Victory
Margin Total Density Distribution
0 10 0.2% 0.2%
1 217 4.27% 4.46%
2 190 3.74% 8.2%
3 782 15.38% 23.57%
4 284 5.58% 29.16%
5 160 3.15% 32.3%
6 293 5.76% 38.07%
7 409 8.04% 46.11%
8 130 2.56% 48.66%
9 93 1.83% 50.49%
10 295 5.8% 56.29%
11 167 3.28% 59.58%
12 83 1.63% 61.21%
13 159 3.13% 64.33%
14 237 4.66% 68.99%
15 83 1.63% 70.63%
16 113 2.22% 72.85%
17 196 3.85% 76.7%
18 107 2.1% 78.8%
19 60 1.18% 79.98%
20 133 2.62% 82.6%
21 133 2.62% 85.21%
22 42 0.83% 86.04%
23 61 1.2% 87.24%
24 108 2.12% 89.36%
25 47 0.92% 90.29%
26 33 0.65% 90.94%
27 85 1.67% 92.61%
28 76 1.49% 94.1%
29 16 0.31% 94.42%
30 30 0.59% 95.01%
31 60 1.18% 96.19%
32 28 0.55% 96.74%
33 13 0.26% 96.99%
34 32 0.63% 97.62%
35 29 0.57% 98.19%
36 8 0.16% 98.35%
37 14 0.28% 98.62%
38 22 0.43% 99.06%
39 5 0.1% 99.15%
40 2 0.04% 99.19%
41 11 0.22% 99.41%
42 11 0.22% 99.63%
43 3 0.06% 99.69%
44 5 0.1% 99.78%
45 3 0.06% 99.84%
46 1 0.02% 99.86%
48 3 0.06% 99.92%
49 1 0.02% 99.94%
51 1 0.02% 99.96%
54 1 0.02% 99.98%
55 1 0.02% 100%
Total 5086 100%

What I hope to convey with this table is how UNEVEN the distribution of margin of victories is.
For example the margin of victory is 3 or 7 23.42% of the time. This shows why sport books are slow to change a point spread to or away from 3 or 7. It also has practical applications in teasers, parlay cards, and buying a half point.
In teasers it is good to cross over the 3 and 7 point margin of victories, for example teasing an 8 point favorite to a 2 point favorite.
With parlay cards it is good to cross the 3 or 7 point spreads, for example if a team is -2.5 on a parlay card but moves to -3.5 that shows a lot of action is falling on the favorite and is a good bet at only -2.5.
With buying a half point it shows the value of buying off of a spread of 3, for example moving a line from -3 to -2.5, although this is seldom allowed off the 3.
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Home Dogs
Table 4 shows how well home underdogs have done against the spread. The fifth column shows the probability of a win, assuming no tie. The sixth column shows the player advantage under the usual 20-cent line (player lays $1.10 to win $1.00). The seventh column shows the player advantage against a 10-cent line (player lays $1.05 to win $1.00).
Table 4: Home Dogs Against Spread
Season Loss Win Tie Pct win EV dime line EV nickel line
1983 31 33 1 51.56% -1.69% 0.69%
1984 42 35 2 45.45% -14.18% -11.52%
1985 35 42 2 54.55% 4.43% 6.65%
1986 36 38 2 51.35% -2.11% 0.26%
1987 32 38 -0 54.29% 4% 6.29%
1988 29 30 1 50.85% -3.17% -0.75%
1989 35 35 1 50% -4.93% -2.46%
1990 32 32 3 50% -4.78% -2.39%
1991 35 42 5 54.55% 4.27% 6.4%
1992 39 44 -0 53.01% 1.33% 3.67%
1993 32 37 4 53.62% 2.47% 4.66%
1994 28 30 4 51.72% -1.29% 0.97%
1995 37 41 1 52.56% 0.38% 2.72%
1996 25 40 -0 61.54% 19.23% 21.15%
1997 33 35 3 51.47% -1.83% 0.49%
1998 33 39 3 54.17% 3.6% 5.8%
1999 40 54 4 57.45% 10.2% 12.24%
2000 37 39 1 51.32% -2.21% 0.19%
2001 35 41 6 53.95% 3.05% 5.18%
2002 36 51 1 58.62% 12.95% 15%
2003 34 37 4 52.11% -0.53% 1.73%
Total 716 813 48 53.17% 1.61% 3.88%

This table is rather remarkable in my opinion. It shows that home underdogs have covered the spread 53.17% of the time, not counting ties. Betting home dogs in every game against a dime line would have yielded a 1.46% profit. Against a nickel line a 3.70% profit.

Home Favorites
Table 5 shows how well home favorites have done against the spread. The fifth column shows the probability of a win, assuming no tie. The sixth column shows the player advantage under the usual dime line (player lays $1.10 to win $1). The seventh column shows the player advantage against a nickel line.
Table 5: Home Favorites Against Spread
Season Loss Win Tie Pct win EV dime line EV nickel line
1983 86 71 7 45.22% -14.39% -11.77%
1984 81 69 1 46% -13.31% -10.63%
1985 63 82 2 56.55% 8.64% 10.78%
1986 82 69 3 45.7% -13.77% -11.1%
1987 60 61 3 43.26% -18.75% -15.97%
1988 84 60 2 48.78% -7.47% -4.94%
1989 82 71 4 46.41% -12.23% -9.62%
1990 70 89 2 55.97% 7.45% 9.63%
1991 70 79 1 53.02% 1.33% 3.67%
1992 72 71 3 49.65% -5.62% -3.15%
1993 86 70 3 44.87% -15.47% -12.77%
1994 88 74 4 45.68% -13.73% -11.08%
1995 85 76 5 47.2% -10.54% -7.98%
1996 82 95 2 53.67% 2.68% 4.97%
1997 88 72 12 45% -14.42% -11.86%
1998 71 94 8 56.97% 9.19% 11.24%
1999 83 74 3 47.13% -10.81% -8.22%
2000 94 79 5 45.66% -13.71% -11.07%
2001 82 60 9 49.38% -5.96% -3.57%
2002 91 82 3 47.4% -10.28% -7.7%
2003 90 93 4 50.82% -3.21% -0.8%
Total 1710 1631 86 48.82% -7.3% -4.8%

This table shows that home favorites have covered the spread 48.82% of the time, not counting ties. So tables 4 and 5 show that dogs in general have been better bets regardless of whether the dog is at home or away. Betting on visiting dogs against a dime would have resulted in a house edge of 2.23%, and against a nickel line of 0.07%.

Away vs Home
Table 6 shows the results of all games against the spread by a home winner, away winner, or tie. The percent columns ignore ties.
Table 6: Home vs Away Against Spread
Season Home Win Away Win Tie Pct. Home Win Pct. Away Win
1983 105 119 8 46.88% 53.13%
1984 105 124 3 45.85% 54.15%
1985 128 100 4 56.14% 43.86%
1986 109 118 5 48.02% 51.98%
1987 100 115 3 46.51% 53.49%
1988 112 117 3 48.91% 51.09%
1989 109 118 5 48.02% 51.98%
1990 123 106 5 53.71% 46.29%
1991 121 107 6 53.07% 46.93%
1992 116 115 3 50.22% 49.78%
1993 109 118 7 48.02% 51.98%
1994 107 119 8 47.35% 52.65%
1995 122 122 6 50% 50%
1996 139 109 2 56.05% 43.95%
1997 110 125 15 46.81% 53.19%
1998 134 105 11 56.07% 43.93%
1999 128 123 7 51% 49%
2000 120 132 6 47.62% 52.38%
2001 124 119 15 51.03% 48.97%
2002 134 128 4 51.15% 48.85%
2003 132 126 8 51.16% 48.84%
Total 2487 2465 134 50.22% 49.78%

So this shows that home teams have done slightly better than away teams.
Dog vs Favorite
Table 7 shows the results of all games against the spread the dog winning, the favorite winning, or a tie.
The percent columns ignore a tie.
Table 7: Dog vs. Favorite Against Spread
Season Favorite Win Dog Win Tie Pct. Favorite Win Pct. Dog Win
1983 102 119 8 46.15% 53.85%
1984 111 116 3 48.9% 51.1%
1985 117 105 4 52.7% 47.3%
1986 105 120 5 46.67% 53.33%
1987 93 118 3 44.08% 55.92%
1988 109 114 3 48.88% 51.12%
1989 106 117 5 47.53% 52.47%
1990 121 102 5 54.26% 45.74%
1991 114 112 6 50.44% 49.56%
1992 110 116 3 48.67% 51.33%
1993 102 123 7 45.33% 54.67%
1994 102 118 8 46.36% 53.64%
1995 113 126 6 47.28% 52.72%
1996 120 122 2 49.59% 50.41%
1997 105 123 15 46.05% 53.95%
1998 127 110 11 53.59% 46.41%
1999 114 137 7 45.42% 54.58%
2000 116 133 6 46.59% 53.41%
2001 115 123 15 48.32% 51.68%
2002 118 142 4 45.38% 54.62%
2003 127 127 8 50% 50%
Total 2347 2523 134 48.19% 51.81%

This shows that dogs against the spread have done significantly better than favorites over the years. Betting all dogs against a dime line would have resulted in a house edge of 1.07%. Betting all dogs against a nickel line would have resulted in a player advantage of 1.12%.

Probability of Victory
The next table is one of my favorites. It shows the probability of an underdog winning according to the point spread. This is based on every game from the start of the 2000 season through week 6 of the 2006 season. The probability of winning was based on smoothing out all the data, and the fair money line is based on that probability.
Probability of Victory in NFL
Point Spread Probability Win Fair Money Line
0 0.5 100
0.5 0.48075 108
1 0.462 116
1.5 0.44375 125
2 0.426 135
2.5 0.40875 145
3 0.392 155
3.5 0.37575 166
4 0.36 178
4.5 0.34475 190
5 0.33 203
5.5 0.31575 217
6 0.302 231
6.5 0.28875 246
7 0.276 262
7.5 0.26375 279
8 0.252 297
8.5 0.24075 315
9 0.23 335
9.5 0.21975 355
10 0.21 376
10.5 0.20075 398
11 0.192 421
11.5 0.18375 444
12 0.176 468
12.5 0.16875 493
13 0.162 517
13.5 0.15575 542
14 0.15 567
14.5 0.14475 591
15 0.14 614
15.5 0.13575 637
16 0.132 658
16.5 0.12875 677
17 0.126 694
17.5 0.12375 708
18 0.122 720
18.5 0.12075 728
19 0.12 733
19.5 0.11975 735

If Buffalo Bills are a 3.5 underdog.
According to table 8 the probability of a 3.5 underdog winning the game is 37.575%.
A fair money line on the Bills is +166 and on the Giants is -166.
This would make the Giants money line just about fair at -165, and the Bills a lousy bet at only +145.
Terminology
Density: Probability that a random variable will be exactly equal to a given value.
Dime Line: The usual sport book standard requiring a bet of $1.10 to win $1.00
Distribution: Probability that a random variable will equal or less than a given value.
Dog: Short for underdog. A team with a probability of losing greater than 50%.
EV: Expected value. How much per unit bet the player can expect to win.
Nickel Line: When the bettor must bet $1.05 to win $1.00. Some casinos offer a nickel line during a "happy hour" ......
Pick: A game with two evenly matched teams with a point spread of 0.