The statistics come from the research firm NPD Group and they were published recently at The Inquirer page. 

This means that 85 per cent of Mac users have a pragmatic approach to their machines and use the best tool for the job at hand, whatever they want when they want it.

The study also revealed what I always suspected, the average household income of those with Macs was around $100,000 and having a Mac was a status symbol. That probably explain why 85% of them also have a PC, Symbols sometime are not enough to live in current modern world controlled by PCs.