Curious about the 3.5% of Productivity statistics

I've seen a few statistics around the internet that only 3.5% of the population is productive. Does anyone know where this comes from and what it means exactly. I've heard people I really respect say that this is the best way to live your life. I don't consider myself a very productive person, but I just want to know where this statistics comes from and what it means exactly. I mean, what is the baseline of what productivity is if you consider yourself productive.