This doesn't talk numbers - but it's a good article.
http://weblogs.foxite.com/joel_leach/2011/10/13/why-microsoft-cancelled-visual-foxpro/

>I don't have any. I don't have the staff to do such world wide market research. But the number you propose is absolutely not believable. Could there be 150,000,000 PCs running some form of a VFP app? Let's say that's the number. But I can't believe that a VFP app was the driving factor that caused those PCs to be purchased.
>
>>So, which figures do you propose?
>>
>>>So, you're attributing the sales of 150,000,000 copies of Windows directly to VFP? That's pure bullsh*t.
>>
>>>>over 300k devs, 500 users/dev
>>
>>>>>So, how did you do it and what number did you come up with?
>>
>>>>>>We did.