mailing list stats?

I'm interested in finding out
* what percentage of email traverses mailing lists
* how this differs in B2B, B2C and C2C communications
* what is the market share of the various (mailing list) providers
  and vendors
* and what are they typically configured to do (in terms of
  modifying the mail)?

Would really appreciate some kind soul sending me pointers
to studies or reports or whatever that publish the above
statistics.

Thanks much