sports betting odds

It is customary with fixed-odds gambling to know the odds at the time of the placement of the wager (the "live price"), although this category also includes wagers whose price is determined only when the race or game starts (the "starting prices"). It is ideal for a bookmaker to price up a book such that the net outcome will always be in his favour, i.e. the sum of the probabilities quoted for all possible outcomes will be in excess of 100%. The excess over 100% (or overround) represents profit to the bookmaker in the event of a balanced book. In the more usual case of an imbalanced book, the bookmaker may have to pay out more winnings than what is staked, or he may earn more than mathematically expected. An imbalanced book may arise since there is no way for a bookmaker either to know the true probabilities for the outcome of competitions left to human effort or to predict the bets that will be attracted from others by fixed odds compiled on the basis of his own personal view and knowledge.
With the advent of Internet and bet exchange betting, the possibility of fixed-odds arbitrage actions and Dutch books against bookmakers and exchanges has expanded significantly. Betting exchanges in particular act like a stock exchange, allowing the odds to be set in the course of trading between individual bettors, usually leading to quoted odds that are reasonably close to the "true odds."
In making a bet where your expected value is positive, you are said to be getting "the best of it". For example, if you were to bet $1 at 10 to 1 odds (you could win $10) on the outcome of a coin flip, you would be getting "the best of it" and you should always make the bet. However if someone offered you odds of 10 to 1 that a card chosen at random from a regular 52 card deck would be the ace of spades, then you would be getting "the worst of it" because the chance is only 1 in 52 that the ace will be chosen. It is mathematically disadvantageous to make a bet where you are getting "the worst of it."
When making a bet where you must put more at stake than you stand to win, you are laying the odds or laying the bet. So, for example, if you bet $1000 that it will rain tomorrow, and if you win you will only win $200 but if you lose you will lose your entire $1000, then you are laying a bet. It is possible that you could be getting "the best of it" or "the worst of it" when you lay a bet; the fact that you are laying a bet does not necessarily mean you are getting "the worst of it". A lay bet is a bet that something won't happen, so if you lay $50 on a horse then you are betting the horse won't win.
Favoured by bookmakers in the United Kingdom and Ireland, fractional odds quote the net total that will be paid out to the bettor, should he win, relative to his stake. Odds of 4/1 ("four-to-one" or less commonly "four-to-one against") would imply that the bettor stands to make a £400 profit on a £100 stake. If the odds are 1/4 (read "one-to-four", or "four-to-one on"), the bettor will make £25 on a £100 stake. Should he win, the bettor always receives his original stake back, so if the odds are 4/1 you would actually receive a total of £500 in return (£400 plus the original £100). Odds of 1/1 are known as evens or even money. Unusually, odds of 10/3 is read as "one-hundred-to-thirty".
Fractional odds are also known as British odds, UK odds or in that country, traditional odds.
Favoured in continental Europe, Australia and Canada, decimal odds differ from fractional odds in that the bettor must first part with their stake in order to make a bet, the figure quoted is the winning amount that would be paid out to the bettor. Therefore, the decimal odds of an outcome are equivalent to the decimal value of the fractional odds plus one. Thus even odds 1/1 are quoted in decimal odds as 2. The 4/1 fractional odds discussed above are quoted as 5, while the 1/4 odds are quoted as 1.25. This is considered to be ideal for parlay betting, because the odds to be paid out are simply the product of the odds for each outcome wagered on. Decimal odds are also favoured by betting exchanges because they are the easiest to work with for trading.
Decimal odds are also known as European odds, or continental odds in the UK.
Moneyline odds are favoured by American bookmakers. There are two possibilities, the figure quote can be either positive or negative.
Moneyline odds are often referred to as American odds. Moneyline refers to odds on the straight-up outcome of a game with no consideration to a point spread.
Positive figures If the figure quoted is positive, the odds are quoting how much money will be won on a $100 wager (this is done if the odds are better than even). Even odds are quoted as $100 . Fractional odds of 4/1 would be quoted as $400, while fractional odds of 1/4 cannot be quoted as a positive figure. Negative figures If the figure quoted is negative, then the moneyline odds are quoting how much money must be wagered to win $100 (this is done if the odds are worse than even). Even odds are quoted as -$100. Fractional odds of 1/4 would be quoted as -$400, however fractional odds of 4/1 cannot be quoted as a negative figure. Most people believe that bookmakers adjust their prices so that they get the same amount of money on both sides of a game. Theoretically, the bookmaker's only financial interest in the bets it accepts is the vigorish it takes from losing wagers, and it simply wants to ensure that the amount of wagers on each side is equal. However, some bookmakers are willing to take more risk and attempt to maximize their bottom line. While having an exactly equal amount of money wagered on each contestant would guarantee themselves a profit and eliminate their risk, that won't necessarily maximize their bottom line. They can make more money when they accept bets at odds which are "inflated" from those which are likely to occur. So for example, if the majority of their customers are going to bet on a team regardless of the price, they will set the price as high as possible. This is called "shading" the line. Generally, the public prefers to back the favorite, and unsophisticated bettors often show up during large events such as the Final Four and the Super Bowl. Some bookmakers actually offer different prices to different customers, using past bets as an indicator of who the customer will bet on as a way of additionally increasing their potential profit. This practice is known in the industry as offering "dual lines".
Traditionally, home advantage in American football betting leads to three points being added to the spread; for instance, if two identical teams, Alpha and Beta, played at Beta's home field, then the spread would be Beta -3 (or, conversely, Alpha +3).
With a match offering a point spread, however, bookmakers must be careful of moving the line too much. Assume, for example, that a large number of Oklahoma betters caused the line to be moved from 27 points all the way to 29 points. If Oklahoma won the game by 28 points, the bookmaker would have to pay both those who wagered that Oklahoma would win by 27 and those who took Kansas on the 29 point spread. Bookmakers refer to such an event as "being middled." This famously occurred in Super Bowl XIII between the Pittsburgh Steelers and Dallas Cowboys, which American bookmakers still remember as Black Sunday. For that game, bookmakers opened Pittsburgh as a 3.5 point favorite, and the line closed just before kickoff at Pittsburgh -4.5. Pittsburgh won the game 35-31, enabling both those who took the Steelers -3.5 and those who wagered on the Cowboys +4.5 to collect.
Sometimes, a point spread is set at an amount that equals a common margin of victory for a particular sporting event. For instance, American football games are often decided by 3 points (the amount awarded for a field goal) or 7 points (the amount awarded for a touchdown with a successful extra-point attempt). In the case of a football game where the favorite is -7, moving the line up or down would likely result in a middle if the favorite wins by exactly 7 points. In this situation, the bookmaker may choose to adjust the return in response to unbalanced action, rather than move the point spread. If the 7 point favorite is getting the most wagers, a bookmaker may reduce the winning return on that team from -7 (-110) to -7 (-120), and increase the winning return on the opposing team from +7 (-110) to +7 (+100). Once this occurs, bettors looking to wager on the favorite will only get a return of $100 for every $120 wagered, while underdog players will get a return of even money for every dollar they wager. The house edge, or vigorish, does not materially change in this instance.
A bookmaker's line can be influenced by one or several large wagers made on a match. Bookmakers pay particular attention to the bets of a professional sports gambler, commonly known within the industry as a "sharp" or "wiseguy." Most bookmakers will not accept bets from bettors they believe fit in this category or otherwise severely restrict how much they are able to stake. Professionals evade such efforts by hiring agents known as "beards" to place bets on their behalf. Groups of professionals who work together are known as a "syndicate." These syndicates will often place large wagers with several books simultaneously, causing the prices to move quickly. Observers refer to these fast line movements as "steam."
Conversely, bettors who are primarily recreational are referred to as "squares". Online, there are certain betting shops that cater more towards sharps and those toward squares. Shops that cater towards professionals generally have higher (or no) upper betting limits and offer lower vigorish, while making some of the money back on fees for withdrawals or minimum bets. Meanwhile, "square" shops generally have lower betting limits and offer more signup bonuses. In return, they charge the standard 11-to-10 vigorish, and offer worse moneylines than the "sharp" shops. In many of the minor sports, sharps make up the majority of bettors, while for large public sporting events such as the NCAA Men's Division I Basketball Championship and the Super Bowl, recreational bettors make up almost 90% of the betting action at sportsbooks, and are the top betting events both in Nevada and online.[1]
Because of how lines move quickly during sporting events, arbitrage betting is possible. Theoretically, this will guarantee a small profit of 1-5% when a person bets on one line at one shop and on the opposite line at another shop. However, a large sum of capital is required for the amount of reward, and great care must be exercised to avoid accidentally betting on the same side at both shops.
Arbitrage situations are commonly found during halftime and intermission periods, where there is a limited amount of time for each bookmaker to determine the line and accept bets. Arbitrage betting is also possible in the weeks and days prior to sporting events as betting lines, especially for American football, are generally set early in a given time period and then adjusted in reaction to betting patterns and other relevant information as the time of the game approaches. Savvy gamblers will sometimes be able to place an early bet using the initial line and a late bet using the later line and then hope that the actual result of the contest falls somewhere between the two bets, thus ensuring either a large win or zero losses.
With the advent of online gambling came odds comparison sites that highlighted arbitrage opportunities by displaying the realtime prices of a number of bookmakers alongside each other. These sites continue to provide the most crucial information to professionals and casual gamblers alike who are looking to bet at the best odds. Also, the above-described practice of dual lines is very common with online bookmakers, and as such may increase arbitrage opportunities.
In general, all forms of arbitrage betting is commonly known as "middling" or "finding the middle" of a particular contest and were fairly common in the early days of organized sports gambling. However, the relatively recent advent of both better communications between the individual sports books, the internet, and more sophisticated linesmaking techniques, has led to fewer opportunities for gamblers to make these types of bets. However with the plethora of new sports bet offerings (many of which are not effectively analyzed by the host bookmaker), arbitrage opportunities continue to exist.
The Federal Wire Act of 1961 was an attempt by the US government to prevent illegal bookmaking