US research firm Markets and Markets published a report recently that estimates the global managed services industry will reach a stunning $256 billion dollars by 2018, representing over 12% compounded annual growth. While the report appears to group managed services from SOHO (small/home office) up to large enterprise, it is one of the few industry studies that actually does not segment the market. 
One of the reasons I do not like most of the managed services reports is they tend to focus too narrowly or they do not provide any definition of their terminology at all. At least this report has the courage to say they include all managed services customer segments, as well as most of the service verticals.
To put this into perspective, Gartner is predicting that global IT spending will reach $3.7 trillion in 2013. Of that amount, roughly $926 billion will come from IT services. Now, the Markets and Markets report says that 2013 managed services spending is around $142 billion. This means that roughly 15% of all “IT services” dollars will be spent on “managed services”. Granted, the comparison is not exact. But, it does give a sense, perhaps for the first time, of how big the managed services marketplace really is. If anything, the percentage is probably on the low side since the Markets and Markets study did not, I believe, take into consideration the influencing effect MSPs have in areas like software and hardware. For example, MSPs can influence hardware and software purchases (on behalf of their customers) without actually having these products ever enter their revenues.
Sure, we’ve always been able to estimate how many MSPs there are but the revenue they were generating was always a grey area for analysts. Now, I believe we have a much better idea of the revenue generated by these MSPs on a global scale.