Britney Spears’s popularity on social networking site Twitter is waning. Last week she was overtaken by Katy Perry on the list of most followed microbloggers and this week she has been eclipsed by Kim Kardashian.

Despite falling to sixth place on the list, the pop star still managed to hit the 9 million followers milestone during the week.

Kim Kardashian and Katy Perry shot past the 9 million mark too as more and more of their fans hit the “Follow” button on Twitter.

Over on Chinese microblogging site Sina Weibo, competition for fourth place has been fierce.

Taiwanese TV host Xie Na rocketed up Weibo’s most followed microbloggers chart from sixth place to fourth place during the week. She leaped over Zhao Wei and Jung Kyung Ho while also surpassing the 8 million followers milestone along the way.

Zhao Wei and Jung Kyung Ho passed 8 million followers too with just a few thousand fans separating them from Xie Na’s fourth place lead.

In September 2010, Twitter had 175 million registered users, while Sina reports that Weibo had more than 140 million registered users in May 2011.

Most popular people on Twitter:

  1. Lady Gaga (12,678,813 followers)
  2. Justin Bieber (11,908,847)
  3. Barack Obama (9,684,984)
  4. Katy Perry (9,182,643)
  5. Kim Kardashian (9,045,135)
  6. Britney Spears (9,026,158)
  7. Shakira (7,684,696)
  8. Taylor Swift (7,529,954)
  9. Ashton Kutcher (7,429,444)
  10. Ellen DeGeneres (7,314,884)

Most popular people on Sina's microblog (Weibo):

  1. Yao Chen (10,713,829 followers)
  2. Dee Hsu (9,688,903)
  3. Kevin Tsai (8,580,386)
  4. Xie Na (8,174,019)
  5. Zhao Wei (8,173,078)
  6. Jung Kyung Ho (8,156,405)
  7. Yang Mi (7,951,814)
  8. Li Bingbing (7,839,241)
  9. Chen Kun (7,442,540)
  10. Huang Jianxiang (6,944,365)