Figuring Dirt Easier Than Turf?

[misscashalot]

Why does the betting public constantly do better
betting low price horses on the dirt than on the turf

Saratoga
Dirt 219 races 84 winning fav 61 winning second rank horses Total .62
Inner Turf 69 races 20 fav 13 second fav Total .48
Main Turf 78 races 21 fav 17 second rank Total .42




BelFall
Dirt 127 races 41 fav 35 second rank horses Total .61
Inner Turf 39 races 11 fav 9 second fav Total .51
Main Turf 39 races12 fav 7 second rank Total .48

[Robert Fischer]

field size will probably close the gap a bit, making the difference less dramatic, but will not be THE answer.

setups and trips are more consistent on dirt. (a bit of a hot topic-)Some may argue that jockeys are more consistent and better judges of pace on dirt as well.

[the little guy]

One reason could be the overall reliability of dirt speed figures as compared to turf speed figures. More likely is the overall percentage of winning the top two choices cover in dirt races versus the top two choices in turf races. This may be related to field size too.

[Ocala Mike]

A very good question, and one which should generate lots of responses.
I am only able to come up with the following intuitive (not scientific) reasons, such intuition based on my own experiences and observations as a horseplayer. In no specific order of importance:

1. Turf races are much more about TRIPS, and less about SPEED. Harder to make "trip" figures than "speed" figures.

2. Related to the above is that turf races are much more JOCKEY STRATEGY races; again harder to reduce to actual numbers.

3. I've always believed, although I don't have the numbers to prove it, that "closers" perform better on the turf than on the dirt. Pure front-runners, when they are the lone speed, are money-makers on the dirt far more than they are on the grass.

4. There are also other variables that are difficult to quantify, such as turf breeding, conformation of hooves ("turf foot"), and probably many, many more items that I am leaving out.

Ocala Mike

[Valuist]

Ground loss tends to be more costly in grass racing and the overall trip is more important.

[ByeByeBuck]

"3. I've always believed, although I don't have the numbers to prove it, that "closers" perform better on the turf than on the dirt. Pure front-runners, when they are the lone speed, are money-makers on the dirt far more than they are on the grass."

I would tend to agree with that. Turf races, a horse, even the favorite or near favorite can be walking alone on the lead, and it doesn't seem to matter, they can quit anyway...but a horse, if it's the favorite or near favorite, if it's on an easy lead alone on dirt usually does well in the stretch.

[misscashalot]

field size will probably close the gap a bit, making the difference less dramatic, but will not be THE answer.

setups and trips are more consistent on dirt. (a bit of a hot topic-)Some may argue that jockeys are more consistent and better judges of pace on dirt as well.

Dirt 7.5 horses per race
Turf 9.6

[Robert Fischer]

Dirt 7.5 horses per race
Turf 9.6

ok so you can use that bit of info to see the random chances for 2 horses out of those field sizes

2/7.5 = .267
2/9.6= .208
-----------------------------------------

FUZZY MATH WARNING:

iF I find the ratio of the RANDOM 2HORSE @ FIELD SIZE d/T .267/.208 =1.28

NOW, If i find the ratio of the ACTUAL 2HORSE RESULTS D/T .62/.48 = 1.29 :kiss:

the brain is a little foggy, and i need a math guy to confirm this but if I am allowed to treat the ratios as such, it would seem that Field Size would be the culprit.

[TrifectaMike]

Assumption that all horses in a dirt race are proven dirt performers and all horses in a turf race are proven turf performers.

Turf races are more chaotic then dirt races. Turf races can be viewed as a race within a race, which makes it more difficult to analyze.

In a dirt race, the chaos occurs early, but the initial order is from a stationary point.

In a turf race, the chaos can occur through out the race and the final chaos is not from a known stationary point, but is a dynamic one.

This makes turf races a far more complex problem.


Mike (Dr Beav)

[rastajenk]

Ground loss tends to be more costly in grass racing and the overall trip is more important.This is a nice, concise explanation. A corollary might be that a higher percentage of turf races are two turns; on the main course, a higher percentage is probably of the one-turn variety. And, as most turf courses are inside the main track, tighter turns contribute to the chances of a troubled trip.

[the little guy]

Once again, the odds of the first two choices in dirt races will equal a higher percentage than the corresponding odds of the first two choices in turf races. That's the reason for the results. The author of the thread helped by showing the significant difference in field size.

It seems people here are debating WHY that is the case.

[TrifectaMike]

Once again, the odds of the first two choices in dirt races will equal a higher percentage than the corresponding odds of the first two choices in turf races. That's the reason for the results. The author of the thread helped by showing the significant difference in field size.

It seems people here are debating WHY that is the case.


I doubt that a small difference in field size amplifies the percentages from turf to dirt. It is a minor impact.

Compare races of identical field sizes and determine if the stats are consistent with varying field sizes.

Mike (Dr Beav)

[classhandicapper]

Aside from everything already mentioned, the average pace on turf tends to be slower than on dirt. A slow pace means that more fresh horses will be in contention at the top of the stretch, which in turn gives more horses a chance to win.

IMO "very" slow paces also tend to reduce the importance of a horse's total energy (overall ability) and increase the importance of its short term late speed.

Sometimes fresh mediocre horses can run really fast for 2-3 furlongs and sneak a win against better overall horses that aren't any faster (or may even be slower) for that short burst.

These pace issues make more close finishes, greater difficulty in separating the horses, and lower win percentages.

As TLG is saying, to a large extent these things are built into the odds.

[TrifectaMike]

Aside from everything already mentioned, the average pace on turf tends to be slower than on dirt. A slow pace means that more fresh horses will be in contention at the top of the stretch, which in turn gives more horses a chance to win.

IMO "very" slow paces also tend to reduce the importance of a horse's total energy (overall ability) and increase the importance of its short term late speed.

Sometimes fresh mediocre horses can run really fast for 2-3 furlongs and sneak a win against better overall horses that aren't any faster (or may even be slower) for that short burst.

These pace issues make more close finishes, greater difficulty in separating the horses, and lower win percentages.

As TLG is saying, to a large extent these things are built into the odds.

Your original post had nothing to do with odds. The odds are a separate matter.

Mike (Dr Beav)

[Valuist]

This is a nice, concise explanation. A corollary might be that a higher percentage of turf races are two turns; on the main course, a higher percentage is probably of the one-turn variety. And, as most turf courses are inside the main track, tighter turns contribute to the chances of a troubled trip.

I think its more than tighter turns. Dirt tracks will occasionally have dead rails. This doesn't happen nearly as much as it used to but how often do you see riders trying to avoid the inner paths on a turf course? I've seen it a few times on Churchill's turf but thats about it. And even then I wondered if the riders' perception of an alleged "dead inside bias" on the turf was more imagined than real.

[misscashalot]

Once again, the odds of the first two choices in dirt races will equal a higher percentage than the corresponding odds of the first two choices in turf races. That's the reason for the results. The author of the thread helped by showing the significant difference in field size.

It seems people here are debating WHY that is the case.

In field sizes up to 7 runners
Only 24 races on the turf
70 on the dirt having 24 winning fav and 19 second choices .61

In field sizes 8 or more
Inner Turf 33 races 8 fav and 8 second choices .48
Main Turf also 33 races 10 fav 6 second choices .48
Dirt 58 races 18 fav and 16 second choices .59

At Bel this meet there seems to be
no difference in winning percentage
of the first 2 bet choices in regard
to field sizes. I'm surprised.
But it's a small sample.

[classhandicapper]

Your original post had nothing to do with odds. The odds are a separate matter.

Mike (Dr Beav)

I didn't make an original post. That was my first post on the subject.

I believe what Andy is saying is that if you look at the average odds of favorites on dirt compared to turf, the dirt favorites go off lower. The same is true of the second choice. So it's natural for dirt favorites to win more often. I agree with him. The rest of it is trying to explain WHY the odds are different. That's where all these trip, pace, field size, and other issues come in. The public recognizes that these turf races are more competitive for a variety of reasons.

[Robert Fischer]

Your original post had nothing to do with odds. The odds are a separate matter.

Mike (Dr Beav)

hey Mike,

over in post 8, is it ok to compare ratios like I attempted?



i like the idea about looking at results in races with a given field size. For example all dirt vs turf races which had exactly "8" runners (or 6,7, or whatever field size was most common of the two sets).

[the little guy]

I didn't make an original post. That was my first post on the subject.

I believe what Andy is saying is that if you look at the average odds of favorites on dirt compared to turf, the dirt favorites go off lower. The same is true of the second choice. So it's natural for dirt favorites to win more often. I agree with him. The rest of it is trying to explain WHY the odds are different. That's where all these trip, pace, field size, and other issues come in. The public recognizes that these turf races are more competitive for a variety of reasons.


Exactly.

I'm not disagreeing, or argueing, with whatever people may be saying....I just think there are two discussions going on. The mathematical reason is that the first two choices, on average, in dirt races will add up to a higher percentage than in turf races. Over time, less takeout, horses will win at a rate extremely close to their odds, thus the the percentage of races won by either the first or second choices will be completely tied to these horses' chances of winning. It's really as simple as that.

As to why the first two choices are at a lower percentage in turf races than dirt, the reasons here all seem valid....but this is the WHY answer in relation to the above answer. Field size, however, has to play a role over time. But, there are obviously other factors, and in general it is that turf racing is more complicated.

[RonTiller]

These are the USA Canada stats for 2011 for favorites:


Surf St Wins Win% ROI IV Avg St
D 38676 14250 36.84 0.83 2.58 7.916433
P 4661 1604 34.41 0.83 2.41 7.939712
T 4867 1554 31.93 0.81 2.55 8.931332

Impact Value is nearly the same for Dirt and Turf. Does a .03 difference in IV really require all the elaborate, sophisticated sounding explanations given in this thread?

Ah, but what if you break it out into sprints and routes?

Routes

Surf St Wins Win% ROI IV Avg St
D 8932 3244 36.32 0.82 2.54 7.657523
P 1513 498 32.91 0.79 2.30 7.740251
T 3092 971 31.40 0.81 2.83 9.022646

Sprints

Surf St Wins Win% ROI IV Avg St
D 29744 11006 37.00 0.83 2.59 7.994183
P 3148 1106 35.13 0.85 2.81 8.035578
T 1775 583 32.85 0.81 2.63 8.772137


Look at Saratoga going back to 2001:

Surf St Wins Win% ROI IV Avg St
2011 D 235 89 37.87 0.91 2.65 7.548936
2011 T 159 42 26.42 0.80 2.38 9.415094
2010 D 207 79 38.16 0.89 2.67 7.710144
2010 T 189 50 26.46 0.74 2.38 9.296296
2009 D 211 65 30.81 0.73 2.46 8.014218
2009 T 165 51 30.91 0.92 2.78 9.315151
2008 D 229 78 34.06 0.78 2.38 7.659388
2008 T 138 38 27.54 0.78 2.48 9.463768
2007 D 195 62 31.79 0.80 2.54 8.307692
2007 T 167 43 25.75 0.73 2.32 9.485029
2006 D 218 74 33.94 0.84 2.38 7.986238
2006 T 133 36 27.07 0.78 2.44 9.413533
2005 D 227 90 39.65 0.91 2.78 7.493392
2005 T 129 37 28.68 0.79 2.58 9.124031
2004 D 249 85 34.14 0.83 2.73 8.200803
2004 T 99 43 43.43 1.24 3.91 9.646464
2003 D 263 106 40.30 0.98 2.82 7.950570
2003 T 91 31 34.07 1.01 3.41 10.043956
2002 D 250 89 35.60 0.89 2.49 7.628000
2002 T 93 22 23.66 0.69 2.13 9.225806
2001 D 221 83 37.56 0.85 2.63 7.855203
2001 T 117 39 33.33 0.82 3.00 9.581196

6 of those years, Turf favorites had a higher impact value than dirt.

Look at Belmont going back to 2001:

Surf St Wins Win% ROI IV Avg St
2011 D 432 155 35.88 0.80 2.15 6.914351
2011 T 330 106 32.12 0.83 2.57 8.742424
2010 D 489 196 40.08 0.87 2.81 7.177914
2010 T 423 123 29.08 0.76 2.33 8.664302
2009 D 597 229 38.36 0.85 2.69 7.184254
2009 T 362 121 33.43 0.84 2.67 8.977900
2008 D 544 194 35.66 0.79 2.50 7.380514
2008 T 408 112 27.45 0.75 2.47 9.382352
2007 D 487 177 36.34 0.81 2.54 7.279260
2007 T 412 131 31.80 0.83 2.86 9.135922
2006 D 597 211 35.34 0.80 2.47 7.264656
2006 T 302 91 30.13 0.80 2.71 9.466887
2005 D 653 244 37.37 0.82 2.62 7.159264
2005 T 285 87 30.53 0.79 2.44 8.824561
2004 D 617 214 34.68 0.80 2.43 7.552674
2004 T 280 91 32.50 0.84 2.93 9.350000
2003 D 654 239 36.54 0.85 2.56 7.620795
2003 T 254 74 29.13 0.78 2.62 9.527559
2002 D 570 206 36.14 0.82 2.53 7.670175
2002 T 290 89 30.69 0.79 2.76 9.327586
2001 D 587 204 34.75 0.79 2.43 7.528109
2001 T 246 72 29.27 0.77 2.63 9.296747

Turf favorites and Dirt favorites IVs flip flopped through the years.

I don't see that there are any strange or anomalous winning favorites by surface phenomena to explain. Sometimes turf favorites do better, sometimes dirt. Depends on your sample dates and sizes.

Ron Tiller
HDW

[TrifectaMike]

Exactly.

I'm not disagreeing, or argueing, with whatever people may be saying....I just think there are two discussions going on. The mathematical reason is that the first two choices, on average, in dirt races will add up to a higher percentage than in turf races. Over time, less takeout, horses will win at a rate extremely close to their odds, thus the the percentage of races won by either the first or second choices will be completely tied to these horses' chances of winning. It's really as simple as that.

As to why the first two choices are at a lower percentage in turf races than dirt, the reasons here all seem valid....but this is the WHY answer in relation to the above answer. Field size, however, has to play a role over time. But, there are obviously other factors, and in general it is that turf racing is more complicated.

The fact that the odds are efficient on average in turf and dirt isn't revelant to why the percentages are different in the context of the question asked.

If someone is serious about the effect of the field size, since we can determine the probability of various field sizes in a sample, we can marginalize the effect of field size. Essentially instead of comparing dirt ,turf and field size, marginalize field size and compare dirt vs turf directly.

Class, my apologizes...got you confused.

Robert, I don't believe it is that simple.

Mike (Dr Beav)

Mike (Dr Beav)

[mountainman]

These are the USA Canada stats for 2011 for favorites:


Surf St Wins Win% ROI IV Avg St
D 38676 14250 36.84 0.83 2.58 7.916433
P 4661 1604 34.41 0.83 2.41 7.939712
T 4867 1554 31.93 0.81 2.55 8.931332

Impact Value is nearly the same for Dirt and Turf. Does a .03 difference in IV really require all the elaborate, sophisticated sounding explanations given in this thread?

Ah, but what if you break it out into sprints and routes?

Routes

Surf St Wins Win% ROI IV Avg St
D 8932 3244 36.32 0.82 2.54 7.657523
P 1513 498 32.91 0.79 2.30 7.740251
T 3092 971 31.40 0.81 2.83 9.022646

Sprints

Surf St Wins Win% ROI IV Avg St
D 29744 11006 37.00 0.83 2.59 7.994183
P 3148 1106 35.13 0.85 2.81 8.035578
T 1775 583 32.85 0.81 2.63 8.772137


Look at Saratoga going back to 2001:

Surf St Wins Win% ROI IV Avg St
2011 D 235 89 37.87 0.91 2.65 7.548936
2011 T 159 42 26.42 0.80 2.38 9.415094
2010 D 207 79 38.16 0.89 2.67 7.710144
2010 T 189 50 26.46 0.74 2.38 9.296296
2009 D 211 65 30.81 0.73 2.46 8.014218
2009 T 165 51 30.91 0.92 2.78 9.315151
2008 D 229 78 34.06 0.78 2.38 7.659388
2008 T 138 38 27.54 0.78 2.48 9.463768
2007 D 195 62 31.79 0.80 2.54 8.307692
2007 T 167 43 25.75 0.73 2.32 9.485029
2006 D 218 74 33.94 0.84 2.38 7.986238
2006 T 133 36 27.07 0.78 2.44 9.413533
2005 D 227 90 39.65 0.91 2.78 7.493392
2005 T 129 37 28.68 0.79 2.58 9.124031
2004 D 249 85 34.14 0.83 2.73 8.200803
2004 T 99 43 43.43 1.24 3.91 9.646464
2003 D 263 106 40.30 0.98 2.82 7.950570
2003 T 91 31 34.07 1.01 3.41 10.043956
2002 D 250 89 35.60 0.89 2.49 7.628000
2002 T 93 22 23.66 0.69 2.13 9.225806
2001 D 221 83 37.56 0.85 2.63 7.855203
2001 T 117 39 33.33 0.82 3.00 9.581196

6 of those years, Turf favorites had a higher impact value than dirt.

Look at Belmont going back to 2001:

Surf St Wins Win% ROI IV Avg St
2011 D 432 155 35.88 0.80 2.15 6.914351
2011 T 330 106 32.12 0.83 2.57 8.742424
2010 D 489 196 40.08 0.87 2.81 7.177914
2010 T 423 123 29.08 0.76 2.33 8.664302
2009 D 597 229 38.36 0.85 2.69 7.184254
2009 T 362 121 33.43 0.84 2.67 8.977900
2008 D 544 194 35.66 0.79 2.50 7.380514
2008 T 408 112 27.45 0.75 2.47 9.382352
2007 D 487 177 36.34 0.81 2.54 7.279260
2007 T 412 131 31.80 0.83 2.86 9.135922
2006 D 597 211 35.34 0.80 2.47 7.264656
2006 T 302 91 30.13 0.80 2.71 9.466887
2005 D 653 244 37.37 0.82 2.62 7.159264
2005 T 285 87 30.53 0.79 2.44 8.824561
2004 D 617 214 34.68 0.80 2.43 7.552674
2004 T 280 91 32.50 0.84 2.93 9.350000
2003 D 654 239 36.54 0.85 2.56 7.620795
2003 T 254 74 29.13 0.78 2.62 9.527559
2002 D 570 206 36.14 0.82 2.53 7.670175
2002 T 290 89 30.69 0.79 2.76 9.327586
2001 D 587 204 34.75 0.79 2.43 7.528109
2001 T 246 72 29.27 0.77 2.63 9.296747

Turf favorites and Dirt favorites IVs flip flopped through the years.

I don't see that there are any strange or anomalous winning favorites by surface phenomena to explain. Sometimes turf favorites do better, sometimes dirt. Depends on your sample dates and sizes.

Ron Tiller
HDW

Hi Ron, admire your work and appreciate the data you can bring to a discussion like this, but do have a question: If the impact value of favorites is higher overall on dirt than turf, how can turf faves post comparatively higher impact values in both sprints AND rts?? It's been a long morning, my eyes are bleery and I'm sure I'm missing something here. Help me out.

[skate]

On turf they move the GATE, from left to right, you can pick up or lose 4 to 6 lengths easy.

When you take your figures for TODAYS Turf, you use figures that dont tell the location of the gate in Previous races.

So unless you keep track of where the gate is located in the PREVIOUS races, you'll gain or lose some lengths when using the current (DRF, for example) figures.

Moving of gate...to keep turf wear even.

[RonTiller]

If the impact value of favorites is higher overall on dirt than turf, how can turf faves post comparatively higher impact values in both sprints AND rts?? It's been a long morning, my eyes are bleery and I'm sure I'm missing something here. Help me out.
Ha...I did the exact same double take on that.

Impact value is calculated from the average field size, and the average field size of turf routes is .25 bigger than turf sprints. So without the breakout by distance, the smaller subset of turf sprints, with a slightly higher win %, is dumped into the pot and those turf routes' larger average field size gets "applied" to the turf sprints in the overall IV calculation, which depresses the overall IV enough to drop below dirt.

That's the best I can figure. Maybe I'm wrong. It is counter-intuitive on the surface, so its not just you. I don't think it is an error, as the SQL is pretty straightforward on all of this.

Ron Tiller
HDW

[raybo]

I think that the fact that turf races are different than dirt races, coupled with the fact that there are far fewer turf races run than dirt, at least in the US, means that the betting public knows more about dirt racing than turf, thus they predict the winners of turf races at a lower frequency than the winners of dirt races.

Maybe that's too simplistic, but that's how I see it.

[classhandicapper]

Ron,

Thanks for that data. Though it seems counter intuitive to me based on observation and experience.

1. I see way more turf races with extreme paces

2. I used to make a lot of "place" bets on short priced horses before net pool pricing and a few other things changed. I did massively better on dirt than turf. It got to the point where I just stopped playing them on turf. It seemed that I would get beat by bad trips WAY more often on turf.

3. In handicapping the races I feel totally lost WAY more often in turf races than in dirt races and at other times on turf the fields seem so evenly matched I'm giving practically all the horses a chance

4. We know that the finishes are closer

So it's hard to imagine field size covers practically all of this. Amazing

[pondman]

Turf is an equalizer.

Turf is easier on horses with rear tarsal joint problems. Injured horses faulter far more on dirt as a whole. Horses not running well because of injuries, which is evident in their past performances, will be thrown out by the crowd. On dirt, this is the correct thing to do. But on grass, a horse with a minor injury is often able to stay with the herd, which make horses closer in ability. The same horse would suffer on dirt.

Infrequently, you see a super grass horse, a Brown Bess, dominate the fields, by going to the front and winning by 8, but that's usually an anomaly. Most turf races result in bunching, which require strategy rather than physical dominance.

[RXB]

Ha...I did the exact same double take on that.

Impact value is calculated from the average field size, and the average field size of turf routes is .25 bigger than turf sprints. So without the breakout by distance, the smaller subset of turf sprints, with a slightly higher win %, is dumped into the pot and those turf routes' larger average field size gets "applied" to the turf sprints in the overall IV calculation, which depresses the overall IV enough to drop below dirt.

That's the best I can figure. Maybe I'm wrong. It is counter-intuitive on the surface, so its not just you. I don't think it is an error, as the SQL is pretty straightforward on all of this.

Ron Tiller
HDW

I get a 2.88 IV in the turf sprint category and a 2.85 overall turf number.

[RXB]

I get a 2.88 IV in the turf sprint category and a 2.85 overall turf number.

In fact, when I calculate the IV's for all categories, I get very different numbers compared to Ron's table:

Total:
D 2.91 P 2.73 T 2.85

Routes:
D 2.95 P 2.82 T 2.83

Sprints:
D 2.78 P 2.55 T 2.88

That's based on the supplied info of winners compared to avg. starters. I suppose that you could get slightly different numbers if you broke each category into separate field sizes and calculated IV's for each specific number of starters-- although I wouldn't think that the overall values would come out all that different. One thing I know for sure: you can't have an IV for a category that is lower than both of the subcategories of which it is comprised, a la the turf category in the original table. An average is always somewhere between the max and min values; mathematically impossible to be otherwise.

[RXB]

In fact, when I calculate the IV's for all categories, I get very different numbers compared to Ron's table:

Total:
D 2.91 P 2.73 T 2.85

Routes:
D 2.95 P 2.82 T 2.83

Sprints:
D 2.78 P 2.55 T 2.88


Oops. I accidentally reversed the route & sprint numbers for dirt and for poly. Corrected below.

Total:
D2.91 P 2.73 T 2.85

Routes:
D 2.78 P 2.55 T 2.83

Sprints
D 2.95 P 2.82 T 2.88