Michelle Malkin posts this morning on mobility in the blogosphere, pointing out that contrary to conventional wisdom, there is actual change in the top ranked blogs over time.

With Michelle's post prompting me, I decided to reach back into the Ecosystem's historical database and check out what the Top 30 ("Higher Beings" and "Mortal Humans") looks like today as compared to six months ago (May 7, 2004).

Here's the result:

Blogs highlighted in green were not in the Top 30 in May, but are now.

So of the current Top 30, nine blogs weren't there six months ago --- just under one third. That certainly isn't a monolithic and static list --- it shows quite significant turnover, really.

In case you are curious, the reason I didn't do this comparison by Traffic rankings is that I only started capturing historical data for traffic about a month ago. But going forward, I'll be able to provide interesting historical reports on traffic, as well as links.

Update: Corrected to show that Matt Yglesias was ranked in the Top 30 in May 2004 as well as November.