The World Boxing Organization (WBO) was formed in 1988 as an offshoot of the WBA. A few Carribbean members disagreed with the rest of the WBA on how to apply the rules, so this makes three out of four majors that is based in Latin America.
It took quite a while for the WBO to become recognized as one of the major sanctioning bodies, and to this day, quite a few people still don't recognize the WBO as a major title. For instance, the Japanese boxing authorities don't recognize the WBO at all, and the IBF does not recognize the WBO has a major title for purposes of formulating its rankings. It's no surprise why it took a long time for this to happen. Right off the bat, they had their initial heavyweight title contested between two complete no-names while Mike Tyson was the undisputed champion of the world, and their titlists (outside of Michael Moorer) tended to be fringe contenders until the mid-90's. However, as certain strong titlists, such as Johnny Tapia, Joe Calzaghe, Marco Antonio Barrera, Naseem Hamed and Dariusz Michaczewski, chose to defend their WBO titles over long periods of time, the belt was lent an air of legitimacy. Today it's considered by most to be just another part of the alphabet soup.
Like most of the other ABCs, the WBO has a number of different titlists and statuses, not all of which make a whole lot of sense:
- Super champion - Unlike the WBA, there's a ton of latitude for the WBO to make super champions, meaning that about half of their "real" champions are super champions. The committee can consider whether the titlist is unified, whether he's made 10 defenses, whether he has a long-term TV contract, the quality of the titlist's record and, for no apparent reason, the titlist's amateur background. Being a super champion means more latitude to face fighters who aren't ranked and a longer time period to face mandatories, and it also means that the person automatically becomes the mandatory if he moves up or down a weight class.
- Regular champion - He's the real titlist, unless there's a super champion. A regular champ may only face fighters also ranked in the WBO's top 15, and must defend his title at least once every 9 months (other than the heavyweight titlist, who inexplicably has 12 months to defend).
- Interim champion - The WBO can declare an interim champion when the super or regular champion is incapacitated, inactive or moving out of the division. Once again, this gives far more latitude than the other sanctioning bodies, and thus interim titlists are named pretty frequently.
- Mandatory challengers - Challengers are appointed by the WBO's championship committee rather than having title eliminators, although the committee may choose to have an eliminator. Also, they're allowed to name two mandatory challengers at the same time. Mandatories are supposed to be the highest ranked available fighter who, if the champ has a long-term TV contract, is acceptable to that network. Anyone who is a mandatory must defend against someone who's ranked in the WBO's top 15 at least once a year to maintain that status.
The WBO title is purportedly more unification-friendly than the other belts - a unification fight or tournament tolls the period for facing a mandatory, and the winner wouldn't need to face the mandatory until 9 months after the unification fight. However, in practice, the belt still rarely remains unified, simply because the other belts tend to have more stringent rules for keeping those belts after a unification, and because a new titlist has certain requirements. However, what makes this more difficult is the WBO's rule that a challenger who first wins the title must face a mandatory challenger within 180 days. This often means that a new WBO titlist who is a 'name' fighter will frequently dump the belt, since it provides little latitude for the fighter to face a big name in his first title defense. The looser rules do, however, mean that when a fighter does unify the WBO title, he usually ends up keeping the WBO title afterwards rather than keeping the other title.
Rather than creating their own ratings criteria, the WBO chooses to use the criteria established by the Association of Boxing Commissions. However, the WBO's rankings have hardly been flawless. Most famously, the WBO not only ranked a dead guy, but actually moved him UP the rankings twice after his death. As far as I know, the WBO hasn't made any changes since then to make sure this type of oversight does not occur. In fact, if you look at their explanations page which discusses why fighters are ranked the way that they are, quite a few ranked fighters are missing their most recent bouts, despite the explanations supposedly being as of June. In addition, since there are only five guys on the rankings committee, there's probably a pretty large world of unknown fighters out there. On their face, the WBO's rankings seem to be absolutely no better than the rankings of any of the other major sanctioning bodies.