0.0001% of 6 billion = 6000 people.
I would say that 6000 people easily control anywhere between 20% and 50% of the worlds wealth. Especially considering that if you research "How many billionaires are there?" You come up with something like this:
"A total of 1,645 people made the 2014 billionaire list, representing combined wealth of $6.4 trillion."
So taking the top 1000 billionaires, or perhaps even the top 100 or so, and then you have the families who really have enough money to control things. These would be the people that are impossible to get much information on, but who definitely hold a lot of sway over the planet.
I think these families are the ones we should be concerned with. Either them or once again a small proportion of them, numbering anywhere between 5 families and 100 families.