As almost every professional bettor will tell you, backing heavy favourites is a sure fire way to the poorhouse. That’s common knowledge, right? Perhaps, but there’s one problem with that sort of thinking: it’s dead wrong.

The received wisdom is the linesmakers skew their odds on heavy favourites since the public love online football betting on the most effective teams. The bookies undoubtedly see a flurry of parlays involving clubs like Chelsea, Barcelona and Juventus every weekend. Surely there is value in taking the underdog in these situations, isn’t there?

In fact, numerous studies have shown that blindly backing long shots is a losing proposition within the long-term. To determine why which is the case, we have to discover how a bookmaker operates. Considering that the bookies take most of their action on short-priced favourites, it’s often assumed they’re exposed to big liabilities if all the hot teams win. While this is sometimes the case, and several bookmakers suffer months of huge losses, there are actually several ways a bookie can protect himself.

You need to take into account that most heavy favourites are combined in parlays involving at least three teams. A bookmaker only needs one loser to take his customer’s money. For this reason, there’s little need to lower the odds on a “public” team. Many sportsbooks will even inflate the odds of a hot favourite to attract new customers, safe in the knowledge that parlay players won’t hurt their bottom line.

Should the favourite’s odds are an accurate reflection of it’s true probability of winning, the bookmaker must make adjustments elsewhere. That usually means offering worse odds on the underdog and also the draw. Comprehending the concept of theoretical hold may make this clearer.

When building lines, a sportsbook will offer odds on each team which give it a slight edge, ensuring a profit regardless of how the game turns out. This is called the Theoretical Hold and is expressed as a share. It represents the combined quantity of customers’ bets that the bookmaker expects to keep.

It’s called theoretical because in reality a bookmaker rarely has balanced action on all sides. If a bookie takes the bulk of his bets on a heavy favourite, he can offer it at a far more generous price and accept a smaller profit margin. Short-priced favourites generally have small margins, but high volumes. Bigger odds mean bigger margins. There is little incentive for a bookie to offer competitive odds on a big underdog if he does not expect much betting interest in that team.