Philadelphia Phillies fans may be the most loyal. The St. Louis Cardinals appear most beloved by women. Fans of the Tampa Bay Rays may be the most devoted after a loss. But A's fans may be the most friendly and social, at least in terms of having the most friends on Facebook.

And in a statistic that may cause Bay Area baseball fans to nod knowingly, fans of the Los Angeles teams, the Dodgers and Angels, are the most bereft of friendship among the 30 major league teams.

On the eve of the 2011 baseball season, Facebook has taken an unprecedented look at the millions of members around the world who have hit the "Like" button for their team, or who posted updates about their feelings about their team after a win or a loss. In findings that could provoke a barroom brawl from Cleveland to San Francisco, the Palo Alto-based social network even developed a "fair weather fan" index for fans who only follow their team when it is winning.

"Baseball is a sport that is particularly about statistics, but you never really see statistics about fans," said Jonathan Chang, the Facebook data scientist who led the social network's anonymous study of baseball fans. "Statistics about fans are just so much more rare to see."

Facebook's study is not based on a random sample, and the findings are limited by being based on information people chose to share. And while estimates of Facebook's U.S. membership are approaching half the total population, the findings are also limited to the social network's membership -- which tends to be somewhat younger than the general population, but also omits everyone younger than 13, according to Facebook's rules.

But by incorporating items like relationships with other fans of the same team, along with age, marital status and physical location, Chang said the Facebook data provides unique insights into a nation divided up not just by red and blue political allegiances but fan communities tied to the baseball clubs.

Some of the Facebook findings echo common perceptions of the teams, but there are also some unique insights into how people connect around their favorite teams. Facebook is releasing the findings Thursday at: www.facebook.com/data.

There is a wide team-by-team range, for example, in the appeal of teams by gender. Nearly 50 percent of fans of the Cardinals and the Minnesota Twins are women, while just more than a quarter of Toronto Blue Jays fans were female. One possible explanation, Chang said, is that baseball has a more universal appeal in U.S. cities than in Canada, where the appeal is more limited to a segment of the population -- men.

Other findings were less surprising. The New York Yankees and the Boston Red Sox have the most extensive "fan Diaspora," as measured by the median distance their fans live from Yankee Stadium or Fenway Park. That's not a surprise to anyone familiar with the "Red Sox Nation" or "Yankees Nation."

Athletics' fans were also among the most scattered across the country and around the world, but Chang said that finding was blunted by the fact that a very high share of fans who "Liked" the A's on Facebook also liked another team. In short, he said, the A's may be the second- or third-choice team of many other baseball fans across the country.

Whether or not the A's ever move to the new stadium in San Jose that owner Lew Wolff would like to build, the team's fans stand out as being among the youngest, most likely to be single, and most male-centric in the major leagues.

And while the average Facebook user has about 150 friends, Athletics' fans were the only fan community to average more than 500 friends on Facebook.

At the other end of the scale, fans of the Angels and the Dodgers have the fewest friends on Facebook, averaging 350 or less.

Philadelphia fans, renowned for their bellicose affection for the Phillies, were least likely to hit the "Like" button for any other team. Well more than 60 percent of Phillies fans "Liked" no other team, compared with less than 5 percent of Washington Nationals fans. In that sense, Chang said, Philadelphia fans might be the most "loyal."

Phillies fans were also the most "provincial," Facebook found, with the highest proportion of their Facebook friends also being fans of the team.

To try to figure out which fans were most loyal to their teams, win or lose, Facebook tracked whether fans posted on Facebook anything about their team on days after a loss or a win. "There is a general tendency to like a winning team," Chang said. "If they are supportive even when their team loses, and they are still posting, then we think they are a stronger fan community."

To incorporate the fact that it's easier to support a winning team, Facebook factored in the winning percentage of teams during the 2010 season. By that index, the least "fair-weather fans" were supporters of the Rays, the Mets and the Reds. The most fair-weather were fans of the Indians, Yankees and Blue Jays -- an observation that might earn you a punch in the nose in Cleveland, where no team has won a championship since 1964.

Perhaps Clevelanders are too depressed about that championship drought to say anything about it on Facebook.

Contact Mike Swift at 408-271-3648. Follow him at Twitter.com/swiftstories.

How A's and Giants fans stack up

  • The Giants were fifth in the majors with 430,000 fans added on Facebook last season, trailing the Yankees, Red Sox, Phillies and Cubs.
  • The A's ranked 27th of 30 teams, with 58,000 fans added.

  • A's fans have the most Facebook friends among major league teams, averaging more than 500 friends per fan.
  • The Giants ranked 16th, with about 400 Facebook friends per fan.

  • The Giants, with just under 15 percent of fans joining during the playoffs, trailed only World Series foe Texas Rangers in adding Facebook fans during the postseason.
  • A's fans were the least likely of any major league team to gain fans on Facebook during the playoffs.

    Source: Facebook