RealGM

Why is it normalized seasonally? Why isn't the raw PER published?

This is just one of many choices Hollinger made along the way based on what he presumably was most interested in. Both the normalized stat that PER is, and the unnormalized version would be of interest to me.

As far as why normalize: Ever years is a different league. Sometimes most subtly, sometimes with rule changes that make certain things easier or harder. When developing statistics I often find that what I want is something that gives an unbiased baseline that I can build my more nuanced understanding into. By normalizing the stat, Hollinger's PER gives us an estimate of how a player stood out compared to his peers without having to think at all about era difference. The consumer of the stat can then project their own feelings about the eras, which is very hard to quantify, to come away with an assessment of how impressive the performances were.