As a fast growing OSN, Weibo attracts hundreds and thousands of people to register as a member. Along with follower number, friend number and message number, there is a time stamp in every user's profile. This time stamp indicates the creating time of this account. As these profiles are contained in a uniform random sample, we can show the growing trend of Weibo by plotting creating time. Figure (A) depicts the number of registered accounts in each month from Aug. 2009 to Oct. 2011 by parsing uniform random sample. It coincides with King-wa Fu' paper that Weibo was first launched in Aug. 2009. It is known that Weibo has the same behaviour with Twitter who is more like a social media other than friendship network. Its main social effect is diffusing the lastest news by the users. The number of registered users in Sep. 2010 breaks the consistency of the overall growing trend. One possible explanation is, in Aug. 2010 a tragic earthquake happened in Qinghai province and this is the first catastrophe since Weibo had been launched. We know that online social media has the advantage over traditional media that the messages spread much faster and since then Weibo played an important role in annoucing messages for help and for searching missing persons. It even became a platform for people to mourn for dead after earthquake.

Subplot (B) is the complementary cumulative distribution function(CCDF) for (A). We can see after the first 18 months' rapid growth period, Weibo starts steadily increasing with around 9% rate each month and this is an extra evidence to support the previous 9% difference between our size estimation with King-wa Fu's.

The creation time of the 1.18 million uniform users could be downloaded here

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