[Watchers of the Web] The evolving form of information on the Web?

["Costello, Roger L." <costello@mitre.org>]

Hi Folks,

There are over 350 different content (MIME) types.  Some common content
types include HTML, XML, GIF, JPG, JPEG, MP3, MPEG, RSS, SVG.

Information exchanged on the Web is in the form of one of these content
types.  (Sometimes an information exchange contains a collection of
items, each item with different content type.)

I would like to know:

Of all the information being exchanged on the Web:
 
what percentage of the information is in the form of the HTML content
type, what percentage of the information is in the form of the XML
content type, what percentage of the information is in the form of the
GIF content type, what percentage of the information is in the form of
the MP3 content type, what percentage of the information is in the form
of the MPEG content type, what percentage of the information is in the
form of the JPG content type, and so forth, for all the content types.

I speculate that the percentages are something like this:

Content type   Percentage
---------------------------
HTML           90%
JPG             2%
JPEG            2%
GIF             2%
MP3             2%
XML             1%
...

However, that's purely my guess.  (What is your guess?)

In addition, I am interested in seeing how the percentage is changing
over time - I am interested in seeing the evolving form of information
on the Web.

Has anyone done such an investigation?

/Roger