Game momentum
CRAZY NBA FACTS FROM THE LAST 14 SEASONS!!!
This 6-article series presents some crazy and interesting findings from all NBA games over the last 14 seasons (from 2002/2003 to 2015/2016).
Today we answer question #3:
Over the past 14 NBA seasons, is there evidence of game momentum?
Suppose you are watching 2 games in parallel:
Game 1: Road1 versus Home1
Game 2: Road2 versus Home2
Assume both games have reached the halftime break, with the following quarter-by-quarter scores:
|
GAME 1 |
Quarter #1 |
Quarter #2 |
GAME 2 |
Quarter #1 |
Quarter #2 |
|
|
Road1 |
25 |
25 |
Road2 |
30 |
20 |
|
|
Home1 |
25 |
25 |
Home2 |
20 |
30 |
As you can see, both games are tied at halftime. Imagine you are told that historically home teams win 55% of games in such a case. In game 1, where the score was tied through quarter #1 and through quarter #2, you would certainly be inclined to say that team Home1 has a 55% chance of winning its game.
But what about Home2’s win probability? They were trailing by 10 points after one quarter, but stormed back to tie the game at halftime with a strong 2nd quarter. What would you tend to say about Home2’s chance of winning the game?
- Significantly higher than 55% since they have momentum;
- Around 55% because there is no such thing as “momentum”;
- Significantly lower than 55% (“counter momentum” effect).
Based on evidence from the past 14 seasons, the answer may come as a surprise to many: it seems like the answer is 3), or maybe 2). But certainly not 1). In other words, “momentum” does not seem to carry over future quarters, it seems to have a counter-effect (perhaps waking up the opposing team)!
Let’s have a look at the numbers from the last 14 NBA seasons. Column #1 in the table below indicates the score at halftime (road team leading by 5, 4, 3, 2, 1, score tied, home team leading by 1, 2, 3, 4, 5). Then, we look at the number of times the HOME team ended up winning or losing in each of three “types” of games:
- The road team had the momentum at halftime;
- Neither team had the momentum at halftime;
- The home team had the momentum at halftime.
How is a team considered as “having the momentum”? If it outscored its opponent by 6 points or more in the previous quarter (in this case: in quarter #2).
If having the momentum truly has an impact and increases a team’s chances of winning a game, we expect to see a bigger home win percentage in “type 3” games compared to the first 2 types. If there is no such thing as momentum, we expect the home win percentages to be fairly similar across all three types. Finally, if NOT having the momentum actually increases your chances of winning (perhaps because it woke the team up), we expect to observe a higher home win percentage in “type 1” games.
|
Score |
Road team had momentum |
Neither team had momentum |
Home team had momentum |
||||||
|
after Q2 |
Wins |
Losses |
Home win % |
Wins |
Losses |
Home win % |
Wins |
Losses |
Home win % |
|
Road by 5 |
64 |
78 |
45,1% |
130 |
208 |
38,5% |
16 |
31 |
34,0% |
|
Road by 4 |
75 |
63 |
54,3% |
149 |
196 |
43,2% |
20 |
17 |
54,1% |
|
Road by 3 |
68 |
68 |
50,0% |
208 |
193 |
51,9% |
25 |
38 |
39,7% |
|
Road by 2 |
73 |
59 |
55,3% |
193 |
178 |
52,0% |
52 |
36 |
59,1% |
|
Road by 1 |
61 |
42 |
59,2% |
281 |
202 |
58,2% |
49 |
52 |
48,5% |
|
Tied |
64 |
41 |
61,0% |
248 |
207 |
54,5% |
47 |
41 |
53,4% |
|
Home by 1 |
56 |
43 |
56,6% |
264 |
188 |
58,4% |
57 |
50 |
53,3% |
|
Home by 2 |
51 |
26 |
66,2% |
287 |
164 |
63,6% |
87 |
68 |
56,1% |
|
Home by 3 |
50 |
35 |
58,8% |
286 |
149 |
65,7% |
90 |
47 |
65,7% |
|
Home by 4 |
43 |
15 |
74,1% |
300 |
147 |
67,1% |
112 |
57 |
66,3% |
|
Home by 5 |
39 |
13 |
75,0% |
291 |
123 |
70,3% |
122 |
46 |
72,6% |
On each row (corresponding to a specific halftime score), we have highlighted in red the highest home win % between the case where the road team had momentum and the case where the home team had momentum. As can be seen above, 9 times out of 11 the win % was greater in the road momentum than the home momentum scenario. Recall we are talking about the home team’s win %, so we are basically saying that the home team wins more often when the road team had momentum (following a 2nd quarter where the road team outscored its opponent by 6+ points)!
Let’s see if we get similar results when considering the score through 3 quarters (instead of 2), and adjusting the definition of momentum consequently as the team outscoring its opponent by 6+ points in quarter #3 (instead of quarter #2):
|
Score |
Road team had momentum |
Neither team had momentum |
Home team had momentum |
||||||
|
after Q3 |
Wins |
Losses |
Home win % |
Wins |
Losses |
Home win % |
Wins |
Losses |
Home win % |
|
Road by 5 |
43 |
91 |
32,1% |
72 |
170 |
29,8% |
18 |
44 |
29,0% |
|
Road by 4 |
44 |
91 |
32,6% |
104 |
176 |
37,1% |
24 |
40 |
37,5% |
|
Road by 3 |
57 |
70 |
44,9% |
131 |
184 |
41,6% |
30 |
39 |
43,5% |
|
Road by 2 |
62 |
65 |
48,8% |
136 |
174 |
43,9% |
33 |
37 |
47,1% |
|
Road by 1 |
58 |
60 |
49,2% |
176 |
176 |
50,0% |
44 |
46 |
48,9% |
|
Tied |
59 |
53 |
52,7% |
213 |
149 |
58,8% |
65 |
48 |
57,5% |
|
Home by 1 |
69 |
34 |
67,0% |
205 |
144 |
58,7% |
66 |
53 |
55,5% |
|
Home by 2 |
62 |
35 |
63,9% |
219 |
108 |
67,0% |
79 |
57 |
58,1% |
|
Home by 3 |
68 |
19 |
78,2% |
217 |
109 |
66,6% |
89 |
52 |
63,1% |
|
Home by 4 |
60 |
17 |
77,9% |
244 |
97 |
71,6% |
106 |
31 |
77,4% |
|
Home by 5 |
44 |
14 |
75,9% |
249 |
85 |
74,6% |
132 |
33 |
80,0% |
This time we obtain 8 cases out of 11 where the home win % is greater in the road momentum as opposed to the home momentum scenario. We notice, however, that there are several cases where the percentages are pretty close to each other, and are therefore probably not statistically different (especially considering the sample sizes which are not very large).
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Thanks a lot for reading! Here is what’s coming up in next articles:
Over the past 14 NBA seasons,