Which sport has the most upsets?

Soccer looks random to my untutored eye and perhaps it is:

Eli Ben-Naim, Sidney Redner and Federico Vazquez at the Los Alamos National Laboratory in New Mexico decided to look at unpredictability of results – how often a team with a worse record overcomes an apparently superior one – as the best measure of how exciting a league is. "If there are no upsets, then every game is predictable and hence boring," says Ben-Naim.

The team analysed results from more than 300,000 games over the last century from the US’s national hockey, football, baseball and basketball leagues and the top English football league. Rugby and cricket were omitted because they do not have a big following in the US.

Their results showed that the "upset frequency" was highest for soccer, followed by baseball, hockey, basketball and finally American football. But when they looked only at data from the past 10 years, the English football Premiership and baseball swapped places, which suggests that soccer might have become more predictable in recent years.

Here is the story.  I have long favored basketball.  In any given year, barring major trades or injuries, only three or four teams (if that) have any chance of winning the title.  You know who the titans are, and you know who the peons are.  Limiting randomness and divvying up the ponds in this fashion boosts suspense and status.  The old Celtics-Lakers match-ups were ideal.  The league is driven by star teams and players, so let’s promote those stars.  Chess has the same property, but a few good pitching nights can turn a World Series around.

The implied prediction is that basketball and football will have large bases of casually informed fans, typically relying on mass media.  Baseball and soccer will have more fanatics, more trivia contests, and will be more deeply rooted in niche media.  You have to know about many players and teams to figure out what is going on, who is likely to win, and why.