Which search engine is worst censor in China?

Press advocacy group Reporters Without Borders has released a report alleging that of the four top search engines operating in China, Yahoo's results are the most heavily censored. Chinese-language editions of Google, MSN, and local competitor Baidu.com were also tested. Snip:

The testing threw up significant variations in the level of filtering. While yahoo.cn censors results as strictly as baidu.cn, search engines google.cn and the beta version of msn.cn let through more information from sources that are not authorised by the authorities.

While Microsoft has just said it does not operate censorship, Reporters Without Borders found that the Chinese version of its search engine displays similar results to those of google.cn, which admits to filtering its content. Searches using a "subversive" key word display on average 83% of pro-Beijing websites on google.cn, against 78% on msn.cn. By contrast, the same type of request on an uncensored search engine, like google.com, produces only 28% of pro-Beijing sources of information. However, Microsoft like Google appears not to filter content by blocking certain keywords but by refusing to include web sites considered illegal by the authorities.

I spent much of the last 30 days traveling in China (and Tibet, a formerly independent nation occupied by the PRC). I wasn't online much, but when I was — mostly from internet cafes out in the sticks — I poked around with some of this myself. I wasn't able to validate or disprove any of RSF's findings, because I wasn't able to spend enough dedicated time doing so. But it doesn't take much searching in Lhasa or Beijing to see that yes, results on all of the search engines cited in this report are filtered for politically sensitive terms and other material. This general observation should come as no surprise to anyone, but it's one thing to hear about it from the comfort of an uncensored connection — and another to be there, experience it, and realize that most internet users in the country don't have the resources or ability to route around internet censorship, which is increasingly enabled by US-based tech firms.

Also, the non-censored Google.com and gmail.com were inaccessible for much of the time I was in the PRC. If memory serves, RSF and others reported this fact in May and June. I saw this to be true for the periods they cited (sometimes for days at a time, sometimes intermittently).

Rebecca McKinnon of Global Voices analyzes RSF's latest China-net-censorship report here, and comes up with different findings on a few of the details. Snip:

My own testing shows that pattern of results to be generally true… but not completely. The MSN service appears to be changing by the day. MSN does seem to block keywords – at least in some cases. For instance, last week when I did a search on MSN Chinese beta for "Tiananmen Massacre" I got a page full of results but also a message disclosing that the results had been filtered. Today when I tried again I got nothing, and no message admitting to filtering the results.

Update: While we're at it, Global Voices just launched a Chinese translation project here. They're looking for Chinese-speaking volunteers, and Rebecca explains:

The GVO Translation Project has two purposes:

First, to relate perspectives from other parts of the world to the Chinese speaking world through translation.

Second, to provide points of view that the mainstream media neglects, so that the Chinese online world can converse with bloggers in other countries.

Update: Reader

Philipp Lenssen says,

I searched Google China for 10,000 words from a dictionary and compiled a list of words for which search result pages were censored based on gov't requests. The footnote and comments explain more on the methodology; e.g. it should be noted that the list does not (not necessarily!) contain typical searches, and it should be noted Google censors based on domains, not words. The word list is nothing more or less than one of the many imperfect ways available to "probe" Google's self-censorship scope — draw your own conclusions from what you see.