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How often do bookmakers make mistakes in setting odds?
Certainly, Zhang has a beautiful record but the majority of those fights are like amateur fights. Not sure why this was recorded on pro.

https://i.ibb.co/PTSbNyb/rosenamajunas.png (https://ibb.co/n3WVbyV)
  https://i.ibb.co/dLB4Zmn/zhang.png (https://ibb.co/0Fqy5sP)

Should the bookmakers consider Rose Namajunas' KOs of those high profiles she busts before setting the odds, you can see it's very close even when she caught Zhang in the first fight.  Currently, it's Rose (1.97)  Zhang (1.87)  on Stake.

I don't think the odds are wrong, Rose Namajunas opened as the slight favorites on other bookies but the line slowly shifted on the side of Zhang probably due to the public trend as most punters expect Zhang to get revenge from their previous fight.

I'd also favor Rose here but I still think it could go either way, so putting the odds at 50-50ish is the correct call from the bookies.

I'm not surprised that the odds were close but I didn't expect the current champ to be the underdog. She's younger with slight advantage on height and reach.

They probably did already. It looks like they put more weight on Zhang's superior striking and TD defense.

Anyway, we understand they factor all usable stats but don't really know their exact formula in setting these odds.

I am not good or know much about fighting matches or other related matches or games, but I know much of football and some other games like horse racing, table tennis, basketball and many like that. What I have noticed about gambling companies is that they are very good at it, they make the odds favour them than to favor punters, this is the reason the companies are always increasing in development and process as many people are losing to them. Do not think they are making any wrong odds in their sportbook and almost all the gambling companies are having almost the same or similar odds in their sportbook. The odds favour the betting companies than the bettors.

This is the correct answer, the public can change the odds given by the casinos, casinos can give very accurate odds but if the public has a completely different view of the odds than the ones they gave then they can force the hand of the casino and force them to adjust their odds, not because they believe anything changes by the people believing a different outcome is more likely, they do so in order to balance their books and to try to obtain roughly the same amount of profits independently of the outcome.

But as far as I know, they set odds according to the likelihood of who will win on the match. Of course, sportsbooks will favor the one who has high chance of winning. But sometimes they don't know also the degree of preparation of each fighter even if we say they consider the age, height, reach and the record. As we have seen in recent boxing matches, there were a lot of upsets. So it means, bookmakers can also make mistakes in choosing who will win the match. Sometimes, the miss also and they can't get the full picture of what may possibly happen in the actual fight.

In my opinion, these chances do not look wrong. I don't know these boxers and from the outside the outcome of this fight seems to me random when I look at their statistics. I think that bookmakers also estimate the odds as 50-50, but set the odds based on the stakes that the public makes. These odds are most likely the result of the usual balancing of accepted bets.

Clicking the chart icon on the far right at bestfightodds:

https://www.bestfightodds.com/events/ufc-268-usman-vs-covington-2-2246

Gives us a betting line history for Rose Namajunas vs Weili Zhang 2:

https://i.ibb.co/74WqJQM/rose-zhang-2.jpg

Line history shows Rose opening as a 1.91. With the line dropping down to 1.80. Then rising back to 1.93.

Line movement depends on the size and volume of bets placed. There are more bets being put on Weili Zhang which causes the line to swing in her favor.

^^ And this is normal bet swing though, I've seen this many times already, so I will go with the majority here that there is no mistakes. There are a lot of gamblers or both side, that's why the odds are swinging like that. And with that said, this fight is going to be close as well, smart bettors where to put their money. But in this case it's almost like 50/50 game.

Before setting odds for a match different parameters will be studied. This is common practice and what we see with the odds of Rose Namajunas vs Zhang Weili can be seen with almost every game. Depending on the supporter response the odds will change. This can be understood when the match goes live. A small marginal difference is found between both the players. On some predictions Zhang makes a lead and in few Rose makes the lead based on comparison. This makes the odds.

I think this isn't really a mistake on the part of the bookmakers. They've probably considered everything before releasing the initial odds. But the betting odds have changed as the gamblers have already started placing their bets.

Namajunas' win over Zhang in their first fight wasn't really a show of better skills inside the octagon. It was more like a lucky head kick that hit Zhang half-unconscious on the floor. So the chance of Zhang beating Namajunas is still there.

They generally pay for their odds feeds so generally they are pretty accurate.

There have been instances of actual mistakes but these are rare and far between.

In general, bookmakers have more info than you. So don't go around thinking that there is a odd mistake when in reality you just may not know as much as the bookmaker does.

I think bookmarkers have their own setting to determine the odds and that could be different, so it is normal if we think that the casino makes mistakes.

You can read on how the bookmarkers calculate odds here:
https://www.onlinebetting.org.uk/betting-guides/how-do-bookmakers-set-odds-and-make-money.html

So I do not think that the bookmarkers make mistakes in setting odds on every match. If we do not like their setting, we can search for the other bookmarkers.

It's a market.

Markets depend on supply and demand to form a price. What you're seeing is simply the market's best guess of the probabilities of each fighter winning.

It doesn't have anything to do with the bookmaker's opinion or whatnot.

Your opinion could well differ from the bookmakers, and if you do have some sort of insight that bookmakers don't know about, that's when you can win in the long run and generate positive EV.

There is no metric that can prove how often bookmakers makes mistake since its unusual and very rare. All there odds set has a basis maybe not on our standards but they some rulebook as guide to follow not just there stats and rank. Maybe on this match they consider the record of both fighter and prioritise the experience over the position of the fighter. This varies depends on the bookmakers setting the odds but this only happened when 2 fighter stats are almost close to each other while both fighters has there own unique advantage to each other.

Don't bookmakers have their own metrics when setting odds? I'd reckon it would be weird for you but it wouldn't be weird for them after all the research they did I suppose. Not familiar with who OP posted about, but researching about the influences of the matches of players should be quite natural in how bookmakers set odds? Sides, considering the fact that you said most fights were amateurish, then with that wouldn't the odds of close to 50-50 be correct? They wrote it down, but the influence is probably small.

Judging by the graph, the volume of bets was within the normal range and the coefficient varied within the usual range.
By the way, I am always confused by such graphs where the zero level is not indicated, if you are not careful, then looking at such a graph you might think that the coefficient dropped almost to zero and then took off again upwards.

Well i would say very rarely as i am betting since years in several sports betting sites both fiat and crypto but i never found mistakes in odds in any of them. Yes some time we feel there is some mistake but that is their calculation and i feel it is our mistake that we feel that they have made a mistake in setting odds but they are the experts.

To me the stats that you have presented look very similar and any possible pricing difference in the betting odds is very marginal at best. You need to remember that unless the betting odds are 2.0 vs 2.0, the bookmaker is making profit on every single decimal point, so they might simply be trying to balance a lot of previous bets that came in with some sort of dynamic pricing model. Now, if you're able to find bets priced above 2.0 on both sides of the equation then THAT is a very mispriced bet and will allow you to make a guaranteed profit. There are definitely people who are trying and successfully making money from this sort of mispricing arbitrage, but they're likely doing it on a scale involving many thousands if not millions of dollars to truly make risk worthy profits.

You never know if a mistake is a mistake... in La Liga Rayo vs Barca was clearly a easy win and the odds were kind of good to bet on a barca win... and it did not happen. Anyway, as a direct answer to your question, not often and not by much. People in the know told me that mistakes happen in games between teams of regional level, not that well known to the bookies and that they include just for completeness and little people bet on.

I'm not a huge fan for the MMA, but I saw some of the fights but not in the female category.
Odds are being set for some reason. There's no way we can identify whether the odds set by the bookies were a mistake or not, because they're as well speculating base on the past data and the current status of each fighter.
I made a short review regarding this and,
It could be that Zhang shows a potential revenge on the 2nd fight. So, the odds will be set not too distant against Namajunas.

Bookmakers start from the 50-50 odds and adjust according to the public bets. This example above shows the effect of the bets on the odds. I'm glad someone posted this as it really helps in clearing up any misunderstandings and people can easily understand how the odds are derived. Nice visual. Mistakes are likely but not that common.

In fact, bookmakers start with completely different odds, not necessarily 50-50. By the way, if I were to choose some kind of graph of the change in odds to visualize the change in the public's mood and the bets made by it, I would choose some other one. In this example, the odds have changed by about 3% in 2 months - it is difficult to call this a significant change. I thought there were examples of a much more dramatic change in odds caused by certain events.

I don't know much about boxing, but I say that in football I've seen some mistakes also in clubs that seemed to be favorites with a much lower probability of winning.
I don't understand these calculations that the houses make, but I've already noticed that some games have much more weight in the statistics that, in my point of view, are calculated wrongly.
I've tried to take advantage of it, but the chances of it happening are so rare it's hardly worth it.

Mistakes do happen from time to time as even bookmakers are normal people and cannot know everything perfectly in detail.They usually rely on some odd providers which mostly are the same for almost all bookmakers with a few variations in their odds.Sometimes mistakes do happen because the staff of a certain bookmaker has the ability to alter these odds and they try to do so and unintentionally may make a mistake

In OP case it is not a mistake,it is that the two contenders have near same probability of winning and that is why odds are almost similar.

Well something else that I read on the internet apparently regarding the price correction:

If bookmakers make any mistake, they usually correct it at the point they realize it. Apparently I read it on the internet that they sometimes even correct them with the revised price even after the event have ended.

I do not think they should be allowed to do that though, if that happens wouldn't it be better if they dissolved the bet?

There is always a personal error possible since it's hard to take thousands of bets everyday and not have 1-2 errors.

Generally they have a policy which covers all of it, lemme quote it :


Soruce :  https://justiceforpunters.org/obvious-bookmaker-errors-palps/ (https://justiceforpunters.org/obvious-bookmaker-errors-palps/)

Even though it has happened, obviously the decision has been made by the bookie, of course I don't see directly the point between Rose and Zhang, but if your question is directed specifically to the question below.


For sure the bookie has a strong indication to determine as I see below.


And the mistakes that bookies often make are:

More clearly you can read here: An obvious mistake made by the bookies (https://www.europeanbusinessreview.com/obvious-mistakes-bookmakers-get-away-with/)