How do sites like Ladbrokes calculate betting odds?
Answers:
Betting odds or betting lines? Betting odds is the price paid on your wager, betting lines is the spread. Both fluctuate with the amount of money taken in by the bookie. The ultimate goal of the bookie is to have equal action on both sides of the contest. The numbers will adjust to encourage bettors to play the side that has less action. This allows the bookie to collect the 'vig' on all of the wagers and not care which side wins. If you need further assistance email me.
How odds are calculated is pretty involved. You have the "money line" and "point spread," not to mention the "vig." I found a good deal of how sportsbooks figure odds on www.online-gambling-made-easy.... This site also has a pretty good glossary of betting terms.
Sportsbooks hire oddsmakers to determine the initial "fair" line (that will generate approximately equal action) with vig factored in. This number then changes depending on which side is generating more action. Odds improve on teams getting less action and worsen on teams getting more action. Again, this is done largely at the discretion of the oddsmakers, though they typically have computer systems to alert them of the current status and what should be done to the line.