# Projection Systems

Baseball is a game filled with numbers -- most of which tell us what has already happened. Those numbers are concrete. If a hitter goes 2-for-5, there's no debating his batting average for the day. He hit .400.

Projection systems use numbers, too, but in an entirely different light. Instead of telling us what has happened in the past, they attempt to tell us what will happen in the future. And while no one would ever claim that any system for projections is 100 percent accurate, their value among teams and fans -- especially fantasy baseball players -- is obvious: We already know what *has* happened. We want to know what *will* happen.

People have been making their own projections subjectively for years. They watch a player and assess his potential, given what they've seen and what they know. But projection systems, on the other hand, attempt to do this objectively -- a much trickier proposition.

How exactly is this accomplished? Well, projection systems take into account a player's age, his past performance -- with recent past weighted heavier -- and a variety of other factors to project how well he might fare over a set amount of time. Different systems apply the criteria differently, but the basic theme is the same: Given how well a player has performed in the past, and given how his numbers will be affected by aging, what should we expect, statistically, from that player in the future?

In this section, you'll find a breakdown of several different types of projection systems, including where they come from and what they represent.

The following are all of the terms defined within this section: