Hanson's idea is that given that "A person's decision will have an affect on the well being of N people" the prior probability that you, and not someone else, is the person who gets to make that decision is 1/N.

What is the crucial difference between being 1 distinct person, of N people making N distinct decisions, and being 1 of N distinct people? In other words, why would the ability to make a decision, that is inaccessible to other decision makers, penalize the prior probability of its realization more than any other feature of distinct world-state?

I will probably have to grasp anthropic reasoning first. I am just a bit confused that if only 1 of N people faces a certain choice it becomes 1/N times more unlikely to be factual.