How many home computer users have microphones on their computers?

I'd like to get a few recent statistics like  . . . "22% of home users in
the U.S. had working microphone on their computer in 2004."

I'd also like to get any stats showing the trend of computers with
microphones. This could be for computer that ship with microphones
(such as laptops) or for microphones that get installed later.

Perhaps data about Skype and other VOIP solutions would be useful.

I'm mostly concerned about home users -- ordinary people.

Thanks for you help.

--BJ