Duke, for instance, has discovered popular topics include its basketball team and research by faculty, particularly with a Chinese connection. Michigan creates its own specialized content in-house for Sina Weibo rather than just translating material from other feeds like Facebook. Many of its followers turned out to be Chinese students on its own campus, so Michigan's using its feed to reach them. But it's had some surprising "hits" in China, too, like the obituary of a Michigan faculty member who was an expert in medical drawings.
Yale reports that photos of its famous architecture — like a recent one of its arresting Beinecke Rare Book and Manuscript Library that Sina retweeted — are popular and deserve credit for at least some of the Yale account's rapid growth.
"People are just going to put a lot of different stuff up and see what sticks," said Nick Pearce, a Durham University sociologist who has been studying how universities use Chinese social media.
Duke has around 3,000 followers; Michigan recently passed 6,000. The University of California-Berkeley had about 11,000 but it hasn't posted anything since last March 21, and a handful of U.K. institutions have passed 25,000.
Then there are two outliers: Peoples' Friendship University of Russia, with more than 170,000 followers, and Yale with about 140,000.
Publicly available software that analyzes Sina Weibo accounts indicates about 95 percent of those following Yale have fewer than 100 followers themselves, and more than 93 percent have made 10 posts or fewer. More than one-third have never posted anything. By comparison, the figures for Zhejiang University, a well-known Chinese institution with a comparable number of followers to Yale, were much lower: only 26 percent have posted 10 times or fewer, and 6 percent have never posted. A recent analysis comparing Yale with Michigan found fewer than 2 percent of Yale's followers post at least once a day on average; at Michigan the figure is nearly one-third.
Experts caution such software may be unreliable, and indeed results varied somewhat. But it also reveals some geographical oddities — though those too are hard to interpret. For instance, it shows roughly 20 percent of Yale's registered from Hunan, a rural province known for its rice farming and chili pepper cooking style, and Yale gets high numbers in other rural areas. But only about 2 percent and 4 percent, respectively, of Yale's followers appear to come from Beijing and Shanghai.
That looks very different from other universities, who typically have heavy concentrations of followers in cities, and a relative handful in places like Hunan (Michigan, for instance, gets more than a quarter of its Sina Weibo traffic from those two cities alone).
"If it is coming from one small (place) that is not likely to have high demand for higher education, something suspicious is going on there," Lane said .
The AP attempted to reach 20 users from a random page of Yale followers. Sixteen of them were not set up to accept private messages, which is unusual on Sina Weibo. Of the remaining four, one had never posted, and two others have not updated since early 2011. The fourth did respond to the AP's attempt to verify the follower's authenticity.
Still, the software suggests some other non-university accounts also have surprisingly large numbers of followers from places like Hunan. Sina's promotion of Yale likely has helped attract real followers. And an analysis performed for the AP by the Beijing-based new media information provider 36Kr.com found Yale had a respectable level of apparently real engagement, with many of its posts attracting comments and reposted by genuine followers.
Morand, the Yale spokesman, and Sid Krommenhoek, who leads Zinch's global business development team, said Yale's reputation at least partly explains the numbers. But both also insisted big numbers aren't the goal.
"It's the big name. It runs deep," Krommenhoek said of Yale. "You kind of expect some schools to grow. It's like, why Yale receives so many applications. But that's not the important thing. The important thing is to find a good fit, to be engaging, and to have a real conversation."
Still, Krommenhoek admits he's flummoxed.
"No one sees this type of growth," he said. "There are a lot of factors. We are very interested."
U.S. universities say Sina Weibo is just a small part of a much larger, long-term strategy to connect with a huge and important country. But one lesson is clear: success can't be judged by sheer numbers.
"In the whole industry, people don't believe in that number anymore," said King-wa Fu, assistant professor of journalism and media studies center at University of Hong Kong.
Pearce, the University of Durham expert, agreed that what matters is quality engagements, not quantity.
"If I was told 'we need 100,000 followers and you'll get a bonus,' I could probably get them 100,000 followers but that wouldn't be real engagement," he said.
Still, Lane, the Albany expert on internationalization by U.S., universities, said the Yale Sina Weibo mystery underscores the risk of the unknown.
"You don't know what you're getting into when you get into other countries," he said. "But when you cross into weibo, it's a world unto itself."
Justin Pope reported from Ann Arbor, Mich. Follow him on Twitter at http://www.twitter.com/JustinPopeAP . Didi Tang reported from Beijing. Follow her on Twitter at http://www.twitter.com/tangdidi.