Q. I know that my Facebook page fan base of 50,000 will result in 12% of advertising I run on site reaching friends of my current fans (FOF). Additionally, I know that with a fan base of 500,000, 40% of my ads will reach FOF. Finally, I also know that 40% is peak amount of performance in this case and that regardless of growth of my fan base, only 40% of my ads will reach FOF.
How do I create a graph or formula that allows me to understand reach of FOF when my fan base is at different levels between 50,000 and 500,000?