Numbers dont match up

According to Pew Research: 8 million American adults say they have created blogs

According to this : Livejournal has 5.5 million users and the combined company (Six Journals !) will have 6.5 million users. 

Doing the basic arithmetic this means Blogger has only 1.5million users.  This is when not counting wordpress, b2, pmachine, Godzilla spaces and so many others. 

What gives Om ? Something doesn't add up here.  What am I missing here ?

Update:

Did some more fact-findings on these blog numbers and its definitely not easing the confusion. How can Livejournal jump to 5.5 million from ~1mill in the span of 5 months !

Excellent analysis of the blog tool market  here at Elise.com