Question about Visitors

I've noticed a huge difference between the stats on any page and the pie chart.

I just put up a new Wizz and the stats say 21 visitors. Pie chart says 4.

The pie chart doesn't record everyone who came.  The stats do.  I think it's something to do with not being able to trace the origins of every visitor, which is the job of the pie chart.  That relies on cookies, which savvy cyber users have disabled. :)

Hah. OK. I guess that makes sense....

Thanks