[Professor-MJ]

Hello everyone, this is my first post on SBR! I've been posting on other websites about my NBA daily projections based on several statistical models I developed over the years. I'm a statistics university professor from Canada, and today I hope to give you some insight about the following question:

Is there evidence of pregame betting line movements having an effect on which team is going to win the game (in the NBA)?

I own a dataset which contains information about all games from the last 14 NBA seasons. I analyzed all games for which data was available on the opening & closing betting lines.

A fictitious bet was placed on the team in favor of which the line moved during the day. For example, assume the opening line has Team A favored to win the game by 5.5 points over Team B. If the closing line went higher, for instance 6.5, I would make a virtual bet on Team A at -6.5. On the other hand, if the closing line went lower, for instance 5.0, I would bet on Team B at +5.0. Notice that I am betting the CLOSING line (which is natural since we are studying whether we should place bets according to how the line moved during the day).

Let’s have a look at the results, where the first column indicates how much the line moved (absolute value of closing line – opening line):

Line movement	Bets won	Bets lost	Ties	Win %
0.5	1631	1673	38	49.4%
1	1131	1159	47	49.4%
1.5	664	669	12	49.8%
2	324	347	10	48.3%
2.5	229	210	6	52.2%
3	122	124	6	49.6%
3.5	49	65	2	43.0%
4	37	52	2	41.6%
4.5	29	24	1	54.7%
5	12	19	1	38.7%
5.5	9	6	0	60.0%
6	10	6	0	62.5%
6.5	7	7	0	50.0%
7	5	4	0	55.6%
7.5	5	2	0	71.4%
8+	20	16	2	55.6%
TOTAL	4284	4383	127	49.4%

A person following the strategy described above would have won 4284 bets, lost 4383 and tied 127, which is good for a 49.4% win percentage. In other words, doing the opposite strategy would have generated a 50.6% win percentage. That is not enough to overcome the bookmaker’s vigorish (i.e. the percentage deducted from a gambler’s winnings as a form of commission).

I have highlighted in bold the win percentages that were below 50%. It is pretty interesting to note that they all occur in the upper portion of the table, which suggest following the plan below:

• a) For smaller differences (4 or less) between opening and closing lines: bet AGAINST the team in favor of which the line moved;
• b) For bigger differences (5.5 or more) between opening and closing lines: bet ON the team in favor of which the line moved.

Over the past 14 NBA seasons, portion a) of the plan above would have generated 4299 winnings bets, 4187 losing bets and 123 tied ones (win % = 50.7%). As for portion b): 56 wins, 41 losses and 2 ties (win % = 57.7%).

A word of wisdom: avoid putting this plan into action. Portion a)’s win percentage is not enough to overcome the vigorish (you need 51.2% at -105 and 52.4% at -110), while portion b)’s sample size is way too small to advocate putting any money on this strategy. But it’s still interesting to see the pattern that occurred here, and you could incorporate this knowledge into your betting strategy.

Now, what if we had had the opportunity to bet the OPENING line? In other words, if by some miracle God gave me a call to let me know in advance that the line was going to move by *x* points in favor of a certain team, how much of an advantage would I get by betting this team? Let's see the numbers:

Line movement	Bets won	Bets lost	Ties	Win %
0.5	1669	1625	48	50.7%
1	1215	1087	35	52.8%
1.5	736	574	35	56.2%
2	358	305	18	54.0%
2.5	265	172	8	60.6%
3	143	106	3	57.4%
3.5	68	45	3	60.2%
4	50	40	1	55.6%
4.5	34	20	0	63.0%
5	18	14	0	56.3%
5.5	11	4	0	73.3%
6	12	3	1	80.0%
6.5	10	4	0	71.4%
7	5	4	0	55.6%
7.5	6	1	0	85.7%
8+	33	4	1	89.2%
TOTAL	4633	4008	153	53.6%

Overall, if you bet a specific team and the line eventually moves in their favor, you have a 53.6% chance of winning. You are in business! Only the case of a half-point movement is not enough to overcome the vigorish: even a 1-point movement yields a winning percentage of nearly 53%. Above 1 point, you are clearly in the driver's seat.

You may argue "that's great, but nobody knows in advance which way the line is going to move". That is true. But I believe those numbers should motivate you to try to anticipate line movements because we have clear evidence that it can be rewarding. When I saw those numbers, I figured maybe I should make my projections the day BEFORE the games occur so that I can possibly take advantage of early lines. Maybe I'll succeed, maybe I'll fail. But we may as well give it a try!

I hope I was able to bring you some value. I'd love to hear your comments about this little study!

Professor MJ

[MikeyPicks1]

Great contribution. Unfortunately for me, though, two years ago I was a victim of one of those 15% chance of losing stats. Caught the number right before Hawks announced they'd sit their starting 5.... Didn't work out that night.
I hope to see more from you Professor MJ.

[wazsx]

which uni prof? Also, players injured and players resting influence the line movement throughout the day. Forecasting the outcome of the games seems much better than line movement, that's just my opinion.

[gojetsgomoxies]

great stuff. thank you......... people talk on here about beating the closing line being the essence of betting to them. so it makes sense if you can pick off good value early off the opening line....

i would think sports where the opening is very clear-cut like weekly football might be very interesting.

i would also think that really big line movements may be because of news so it's not really open to close movements.

you are probably aware of this but moscowitz sp? did a giant financial paper on sports betting.......... i found it very confusing and i read alot of quant papers.

[IBetYou]

He's a pretend professor, like Glenn Rivers is a pretend doc.

1st bit interesting, 2nd bit redundant -reason being that line movements are almost entirely due to injuries. If you can predict which players will sit out then great/ you can make money, but I don't need a professor to tell me that.

[Professor-MJ]

Great contribution. Unfortunately for me, though, two years ago I was a victim of one of those 15% chance of losing stats. Caught the number right before Hawks announced they'd sit their starting 5.... Didn't work out that night.
I hope to see more from you Professor MJ.

That's pretty unfortunate! How did you get the info before the public did? Also, how much time elapsed before line adjusted after you placed your bet?

[Professor-MJ]

which uni prof? Also, players injured and players resting influence the line movement throughout the day. Forecasting the outcome of the games seems much better than line movement, that's just my opinion.

Laval University (Quebec City, Canada).

[Professor-MJ]

great stuff. thank you......... people talk on here about beating the closing line being the essence of betting to them. so it makes sense if you can pick off good value early off the opening line....

i would think sports where the opening is very clear-cut like weekly football might be very interesting.

i would also think that really big line movements may be because of news so it's not really open to close movements.

you are probably aware of this but moscowitz sp? did a giant financial paper on sports betting.......... i found it very confusing and i read alot of quant papers.

Big line movements are definitely the result of injured players news. But 0.5, 1, 1.5, 2 point movements can be attributed to anything, in my opinion.

[coolguy73739]

Sorry but Study of Line movement has no meaning unless you know that big WHY as to why line is moving in a particular direction..
My research is based on that WHY that I have been searching for last 3-4 years....
The inside information holds crunch value in NBA since there are so many meaningless games out of 82 that each team has to play and Bookies have plenty of those..( inside info imo)...
Today's HOU line movement from PK to -4 is for a reason and I think I know that WHY to certain extent and hence playing big on NOP +4 today..
Good luck Sir!

[MikeyPicks1]

One of those lucky things. The obvious question was to middle, or not. I chose to not.

[Professor-MJ]

Sorry but Study of Line movement has no meaning unless you know that big WHY as to why line is moving in a particular direction..
My research is based on that WHY that I have been searching for last 3-4 years....
The inside information holds crunch value in NBA since there are so many meaningless games out of 82 that each team has to play and Bookies have plenty of those..( inside info imo)...
Today's HOU line movement from PK to -4 is for a reason and I think I know that WHY to certain extent and hence playing big on NOP +4 today..
Good luck Sir!

Thanks for the reply. The Rockets line movement all happened yesterday (around 5pm they were already 3.5-point favorites, so it didn't remain pick'em for very long). Would you be willing to let us know why you believe the line moved in this particular case?

[coolguy73739]

Thanks for the reply. The Rockets line movement all happened yesterday (around 5pm they were already 3.5-point favorites, so it didn't remain pick'em for very long). Would you be willing to let us know why you believe the line moved in this particular case?

Cousins/Davis combination is the least I can say at this stage.. GL!

[gojetsgomoxies]

hey, i love quebec city

have you read moskowitz sports trading paper? i'd have to spend days reading it. it did seem to suggest - to me at least - that closing spreads aren't the holy grail people here think they are.

[wazsx]

Laval University (Quebec City, Canada).

im at Concordia University

[Snowball]

Thanks for the work.

I don't see any value in fading the LM (line movement) as a betting strategy,
the effort is not worthwhile at this tiny percent differential. Surely it is not worth
the time, and other strategies are superior.

There is a lesson to be learned, however; namely that the "public" short move LM
based on an abundance of dollar volume is never a phenomenon worth chasing.
Hence, don't chase steam unless it is connected with major news, such as a player injury,
if at all - spend more time looking into other options than line movement as an indicator
or tool in prediction models.

That's right, there are better ways to predict outcomes, and better bankroll strategies
- and better ways to understand sport (as opposed to just math) - which are more worthwhile
pursuits to profits.

I know of "handicappers" on SBR in the years I've been here who really do no more
than watch LM all day - and base their selections on this. You've debunked that
concept once and for all, it is a pointless excercise and I've known this for many
years, but you've proven it. (in the NBA, at least).

[Professor-MJ]

hey, i love quebec city

have you read moskowitz sports trading paper? i'd have to spend days reading it. it did seem to suggest - to me at least - that closing spreads aren't the holy grail people here think they are.

No never read it. Interesting, I need to grab this paper!

[gojetsgomoxies]

http://faculty.som.yale.edu/Tobiasmo...rtsBetting.pdf

[Professor-MJ]

Thanks for the work.

I don't see any value in fading the LM (line movement) as a betting strategy,
the effort is not worthwhile at this tiny percent differential. Surely it is not worth
the time, and other strategies are superior.

There is a lesson to be learned, however; namely that the "public" short move LM
based on an abundance of dollar volume is never a phenomenon worth chasing.
Hence, don't chase steam unless it is connected with major news, such as a player injury,
if at all - spend more time looking into other options than line movement as an indicator
or tool in prediction models.

That's right, there are better ways to predict outcomes, and better bankroll strategies
- and better ways to understand sport (as opposed to just math) - which are more worthwhile
pursuits to profits.

I know of "handicappers" on SBR in the years I've been here who really do no more
than watch LM all day - and base their selections on this. You've debunked that
concept once and for all, it is a pointless excercise and I've known this for many
years, but you've proven it. (in the NBA, at least).

Thanks for the insight, I'm glad I could help prove basing your picks only on line movement is indeed pointless and hopeless.

[Professor-MJ]

http://faculty.som.yale.edu/Tobiasmo...rtsBetting.pdf

Thanks, I'll have a look when I get a chance.