What is Exchange Server’s market share?

I had this question asked by a large Midwestern university medical center with regards to health care penetration of Exchange.  Here is what I dug up from a Ferris study of over 900 businesses representing 10.6 millions messaging users:

Exchange:

• Exchange has about 65% market share across all organizations.
• It has a 75% penetration in health care businesses with more than 5,000 employees.
• Exchange does very well in telecommunications industries with at least 1,000 employees, where it has a 90% penetration.
• Almost all organizations with up to 49 employees are on Exchange 2007. More than 40% of Exchange seats in organizations with over 10,000 employees are on Exchange 2003. About 5% of Exchange-using organizations with up to 500 employees are on Exchange 2003. Exchange 5.5 has almost disappeared.

The study is here: http://www.ferris.com/?p=318858

While we are talking data points, I found some interesting information around OCS from Gurdeep Sing Pall, Corp VP of UC:

• Our customers tell us that OCS slashes their overall telephony costs by 30 to 60 percent, with their long distance charges reduced by up to 76 percent, and almost one-third sliced off their mobile telephony overhead.
• More than half of Fortune 500 companies have deployed UC technologies