Sports betting is the general activity of predicting sports results by making a wager on the outcome of a sporting event.
Perhaps more so than other forms of gambling, the legality and general acceptance of sports betting varies from nation to nation.
In North America, for example, sports gambling is generally forbidden, while in many European nations, bookmaking
(the profession of accepting sports wagers) is regarded as an honorable occupation and, while highly regulated, is
not criminalized. Proponents of legalized sports betting generally regard it as a hobby for sports fans that increases
their interest in particular sporting events, thus benefitting the leagues, teams and players they bet on through higher
attendances and television audiences. Opponents fear that, over and above the general ramifications of gambling,
it threatens the integrity of amateur and professional sport, the history of which includes numerous attempts by sports
gamblers to fix matches, although proponents counter that legitimate bookmakers will invariably fight corruption just as
fiercely as governing bodies and law enforcement do.
Types of bets
Aside from simple wagers--betting a friend that one's favorite baseball team will win its division, for instance, or buying a football "square" for the Super Bowl--sports betting is commonly done through a bookmaker. Legal sports bookmakers exist throughout the world (perhaps most notably in Las Vegas). In areas where sports betting is illegal, bettors usually make their sports wagers with illicit bookmakers (known colloquially as "bookies") and on the Internet, where thousands of online bookmakers accept wagers on sporting events around the world. (In the United States, the legality of Internet wagering is ambiguous, due to the fact that online bookmakers generally operate outside of the U.S. Many online bookmakers do not accept wagers from the U.S. due to these unresolved legal questions.) The bookmaker earns a commission or "vigorish" by regarding the money at risk as less than the size of the bet placed. A common line is a $110 bet on a fair coin which pays $210 to win and $0 to lose. On this line, it costs $220 to bet both sides of the same coin simultaneously, but the combined bet always pays $210. The $10 loss constitutes the vig. There are opposing positions on whether the winner or loser can be construed as paying the vig, but this debate is not especially meaningful. If you view $110 to win $210 on a fair coin as $100 at risk, then it will appear as if the loser pays the vig; if you view the same line as $110 at risk, then it will appear as if the winner pays the vig. It happens that standard practice among bookies is to adjust odds so the amount at risk remains constant from the winning side of the proposition, hence the common perception that the loser pays the vig. Vigs expressed as percentages suffer from the same perceptual bias. On the line as given in this example, for a fair coin, the bookie has an expectation of making $5 for each $110 bet placed, which is often divided out and expressed as 4.5% Odds on teams or opponents are quoted in terms of the favorite (the team that is expected to win, thus requiring a riskier wager) and the underdog.
Bookmakers generally offer two types of wagers on the winner of a sporting event: a straight-up or money line bet, or a point spread wager. Moneylines and straight-up prices are used to set odds on sports such as soccer, baseball and hockey (the scoring nature of which renders point spreads impractical) as well as individual vs. individual matches, like boxing. For these sports, bookmakers in Europe and Asia generally use straight-up odds, which are quoted based on a payout for a single bet unit; for example, a 2-1 favorite would be listed at a price of 1.50, whereas an underdog returning twice the amount wagered would be listed at a price of 3.00.
American bookmakers generally use moneylines, which are quoted in terms of the amount required to win $100 on a favorite, or the amount paid for a $100 bet on an underdog. The amount "won" in a bet is the net amount over and above the initial bet. If a person wins $200 on a bet of $100, the bookmaker actually pays the winner $300 (i.e. $200 plus the initial bet of $100).
For example, a baseball game between the St. Louis Cardinals and Chicago Cubs might have a moneyline on St. Louis (the favorite) at -200 and Chicago (the underdog) at +180. A bettor looking to take St. Louis must risk $200 for every $100 he wishes to win over and above the initial $200 bet. A person wagering on Chicago will win $180 for every $100 he bets.
The +180 moneyline on Chicago includes a 20 cent "dime line". Bookmakers generally use a "dime line" with moneylines to calculate the vigorish they receive on losing wagers. Without the 20 cent dimeline in the example above, the Chicago moneyline would be +200.
For favorites of -120 to -150, the difference between the favorite and underdog is 10 cents; i.e., the underdog to a -120 favorite is priced at +110. The discrepancy between prices rises for favorites of -160 or higher.
Unlike point spread bets, a moneyline wager requires only that the team wagered upon win the match. In sports such as baseball, where certain teams can be heavy favorites against weaker opponents (sometimes as much as -350 or higher), the moneyline system requires that a hefty sum be risked on the favorite, while enticing underdog players with a higher payout.
In sports such as basketball and American football, rather than varying the money odds (which can be substantial in lopsided matches), the point spread is used. A point spread wager typically requires a bettor to risk $110 to win $100, the extra $10 being the bookmaker's vigorish if the wager loses. However, bettors backing the favorite collect only if their team wins by more than a specific victory margin, which is set at the time of the wager. Similarly, underdog bettors can collect even when their team loses, as long as they cover the point spread by losing by fewer points than were quoted by the bookmaker. For example, suppose that a college football game between Oklahoma and Kansas had Oklahoma as a 27 point favorite (quoted as Oklahoma -27, or Kansas +27):
If Oklahoma defeats Kansas by more than 27 points, bettors on Oklahoma would receive $100 on a $110 bet. Kansas bettors lose the $110 they wagered.
If Kansas defeats Oklahoma, bettors on Kansas would receive $100 on a $110 bet. Oklahoma bettors lose the $110 they wagered.
If Kansas loses by less than 27 points, they have covered the spread. Bettors on both sides are then treated exactly as if Kansas had won the game.
If Oklahoma wins by exactly 27 points, the wager is called a "push", and neither side wins. Standard practice by U.S. bookmakers is to return the stakes of all bettors on the game in full. To prevent pushes and ensure that they receive their commission on losing wagers, bookmakers often set point spreads that include a half-point.
Another common wager available for sporting events involves predicting the combined total score between the competing teams in a game. Such wagers are known as "totals" or "over/unders." For example, the Oklahoma/Kansas football game described above might have a total of 55 points. A bettor could wager that both teams will combine for over 55 points, and play the "over." Or, she could predict that the score will fall under this amount, and play the "under." As with point spreads, bookmakers frequently set the totals at a number involving a half-point (i.e., 55.5), to reduce the occurrence of pushes.
Many bookmakers offer several alternative bets, including the following:
Proposition bets. These are wagers made on a very specific outcome of a match. Examples include guessing the number of goals each team scores in a soccer match, betting whether a wide receiver in a football game will net more or less than a set amount of total yardage, or wagering that a baseball player on one team will accumulate more hits than another player on the opposing team.
Parlays. A parlay involves multiple bets (usually up to 12) and rewards successful bettors with a large payout. For example, a bettor could include four different wagers in a four-team parlay, whereby he is wagering that all four bets will win. If any of the four bets fails to cover, the bettor loses the parlay, but if all four bets win, the bettor receives a substantially higher payout (usually 10-1 in the case of a four-teamer) than if he made the four wagers separately.
Run line, puck line or goal line bets. These are wagers offered as alternatives to straight-up/moneyline prices in baseball, hockey or soccer, respectively. These bets feature a fixed point spread that offers a higher payout for the favorite and a lower one for the underdog. For example, the above-described Cardinals/Cubs baseball game might offer a run line of St. Louis -1.5 (+100) and Chicago +1.5 (-120). A bettor taking St. Louis on the run line can avoid risking $200 to win $100 on the moneyline, but will collect only if the Cardinals win by 2 runs or more. Similarly, a run line wager on the Cubs will pay if Chicago loses by no more than a run, but it requires the bettor to risk $120 to win $100.
Future wagers. This bet predicts a future accomplishment by a team or player. One example is a bet that a certain NFL team will win the Super Bowl for the upcoming season. Odds for such a bet generally are expressed in a ratio of units paid to unit wagered. The team wagered upon might be 50-1 to win the Super Bowl, which means that the bet will pay 50 times the amount wagered if the team does so.
Most people believe that bookmakers attempt to "balance" their action, by adjusting 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. In reality, however, bookmakers 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.
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 the 1979 Super Bowl 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 vigorish in response to unbalanced action, rather than move the point spread. If the 7 point favorite is getting the most wagers, a bookmaker may change the vigorish on that team from -7 (-110) to -7 (-120), and move the underdog to +7 (+100). Once this occurs, bettors looking to wager on the favorite must risk $120 for every $100 they wish to win, while underdog players will get even money for every dollar they wager.
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." Some bookmakers will not accept bets from bettors they believe fit in this category. As a result, professionals use "beards" to make the bets for them. 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.
Because of how lines move quickly during sporting events, arbitrage betting is possible. Theoretically, this will guarantee a small profit of 3-6% 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.
The Federal Wire Act of 1961 was an attempt by the US government to prevent illegal bookmaking.
Historically, sports betting has been associated with a number of unsavory characters, which has a lot to do with its desultory legal treatment throughout the world. Organized crime notoriously has relied upon sports betting for money laundering or funding purposes. The corruption or threat of a boxer to take a dive at the x round is a frequent theme in mafia-related movies. All of the American professional sports leagues, as well as the National College Athletic Association (NCAA), take stringent measures to disassociate themselves from sports gambling. Nevertheless, sports history is riddled with several incidents of athletes conspiring with gamblers to fix the outcomes of sporting events, or criminals acting against athletes whose on-field performance affected their wagers.
In 1919, gamblers bribed several members of the Chicago White Sox to throw the World Series. This became known as the Black Sox Scandal and was recounted in book and movie form as "Eight Men Out".
In 1978, mobsters connected with the New York Lucchese crime family, among them Henry Hill and Jimmy Conway, organized a point shaving scheme with key members of the Boston College basketball team.
Andres Escobar, a Colombian defender, was murdered shortly after his return from the 1994 FIFA World Cup, where he scored an own goal, the first of a 2-1 defeat to the USA that knocked out the Colombians at the first phase. In the most believed explanation, the Medellin drug cartel bet large sums of money that Colombia would advance, and blamed the Medellin-born Escobar for the loss.
In 1994, a comprehensive point shaving scheme organized by campus bookmaker Benny Silman and involving players from the Arizona State University men's basketball team was uncovered with the assistance of Las Vegas bookmakers, who grew suspicious over repeated large wagers being made against Arizona State.
On 10 February 1999, a plot to disable the floodlights of The Valley during a Charlton-Liverpool match was discovered. Three individuals were arrested, and the scam tracked to Malaysia, where the Premiership is very popular, and bets frequent.
In early 2000, Hansie Cronje, then highly-regarded captain of the South African cricket team, rocked the cricketing world with frank admissions of match-fixing. Hansie admitted to receiving more than $140,000 USD from London-based bookies to influence aspects of his team's performance. For example, he convinced Herschelle Gibbs to score less than 20 runs in a One Day International for a $15,000 USD reward. Hansie received a lifetime ban from any involvement in professional cricket but he maintained throughout his numerous trials that he never consipired to fix overall match results. He died tragically in a plane crash in 2002, leaving behind many unanswered questions and a tainted legacy.
In late 2004, the game between Panionios and Dinamo Tbilisi in the 2004-05 UEFA Cup was suspected of being fixed after British bookmakers detected an unusually high number of half-time bets for a 5-2 win for the Greek side, which was trailing 0-1. As the final result ended up being 5-2, suspicions of fixing quickly emerged, but were quickly denied by both clubs, although UEFA started an investigation. 
The Italian Football Federation said in October 2000 it had found eight players guilty of match-fixing. Three were from Serie A side Atalanta and the other five played for Serie B side Pistoiese. The players were Giacomo Banchelli, Cristiano Doni and Sebastiano Siviglia (all Atalanta) and Alfredo Aglietti, Massimiliano Allegri, Daniele Amerini, Gianluca Lillo and Girolamo Bizzarri (all Pistoiese). The charges related to an Italian Cup first round tie between the two sides in Bergamo on August 20, 2000 which ended 1-1. Atalanta scored at the end of the first half and Pistoiese equalised three minutes from full time. Atalanta qualified for the second round. Snai, which organises betting on Italian football, said later it had registered suspiciously heavy betting on the result and many of the bets were for a 1-0 halftime score and a fulltime score of 1-1.
In early 2005, the German Football Association (DFB) revealed that referee Robert Hoyzer was under investigation for suspected betting on a first-round German Cup tie between regional league side Paderborn and Bundesliga club Hamburger SV in August 2004, and possibly fixing the match. In the match, HSV took a 2-0 lead, but Hoyzer sent off HSV striker Emile Mpenza in the first half for alleged dissent (a sending-off that many observers considered unwarranted), and later awarded Paderborn two dubious penalties. Paderborn went on to win 4-2. Several days later, Hoyzer admitted to having fixed that match, as well as several others he worked. He went on to implicate other referees and several players in the scandal. Hoyzer himself was arrested on February 12 after evidence emerged that he may have fixed more matches than he had admitted to fixing. On February 16, UEFA announced that it would send an investigator to Athens to investigate possible links between this scandal and the aforementioned Panionios-Dinamo UEFA Cup tie. Eventually, Hoyzer was sentenced to 2 years and 5 months in prison. The Croatian betting syndicate which had paid Hoyzer to fix matches was also found to be linked to the Panionios-Dinamo match.
In late September 2005, two referees (Edilson Pereira de Carvalho and Paulo Jose Danelon) were accused of fixing several matches in the Sao Paulo championship for an internet betting ring that moved over USD100,000 on each match day, receiving around USD 4,400 for each match . In the following days, Armando Marques, president of the national commission of referees resigned and Nagib Fayad and Vanderlei Pololi, two businessmen, were arrested as suspects of working as middlemen between the referees and the corruption ring. In early October, a court ordered that the matches where Carvalho was the referee would have to be replayed and free to the public. No decision was made about Danelon's matches.
Sports betting forums
The Internet not only revolutioned the ability to bet online, but also the ability to communicate with like-minded bettors. Sports betting forums offer lively give and take where bettors discuss their predictions about games and help one another decide on profitable bets.
Betting in fiction
Spoiler warning: Plot and/or ending details follow.
In the 1989 film Back To The Future Part II, after Marty and Doc travel to 2015, the old Biff Tannen takes a Sports Almanac back in time to give it to himself in 1955, advising his younger self to use it for betting on any forthcoming sports events up until 2000. Younger Biff does and becomes a millionaire, which creates an altered version of time which Marty and Doc encounter when they return to 1985. In order to restore the damage done from the bets, they need to travel to 1955 and destroy the almanac before it is ever used.