Understanding Salary Caps and Why The NFL opted out

OK, maybe I can't say for certain why the NFL opted out of their current CBA. But what I can speak to is the problem with salary caps as they are structured in the NHL, NFL and NBA, so that sports fans can understand why the NFL is doing what it is doing and why it could and probably will happen in any league governed by a salary cap. The basic structure of a salary cap is that the revenues of the league are aggregated into a total pool, call it football, basketball or hockey related income. E