Researchers at Carnegie Mellon University have published a report showing that the Chinese government is censoring more internet content than previously believed.
Lead author David Bamman said Chinese censors blocked 16% of the 57 million microblog posts he monitored.
The posts were censored for a variety of reasons. Some were spam, others were pornographic, but Bamman said the most highly deleted terms were political.
"They include things like Falun Gong, which is a banned spiritual movement in China, political activists like Ai Weiwei, former Chinese leaders," said Bamman, a Ph. D. student in CMU's Language Technologies Institute.
The raw data for the study came from the Chinese microblog site "Sina Weibo" in the late summer of 2011.
The study said some seemingly innocuous terms were censored as well. For example, Bamman said several topics were restricted after the spread of a false rumor that said iodized salt could prevent radiation sickness from the Fukushima disaster in Japan.
"People went to the stores and bought up all this iodized salt, believing that it could help prevent radiation poisoning," said Bamman. "They caused a run to such an extent that the government came down and told people not to believe these rumors, and it's around this time that we start seeing a lot of terms relating to iodized salt, radiation poisoning being deleted in messages on Sino Weibo."
The study author said he doesn't see that as an overreach by the Chinese government.
"It does provide an example of how sometimes censorship can be used for beneficial purposes," Bamman said. "It's not entirely a nefarious system, as we generally think."
Bamman said his technique of monitoring massive amounts of web pages could be used to keep an eye on Twitter censorship. In January, Twitter announced it will allow governments to censor tweets as they see fit.