THE BOOK--Playing The Percentages In Baseball

Tuesday, January 22, 2008

Win Shares Aging Curves

There’s probably no bigger detractor of Win Shares than I am.  Still, when you have aggregated data, alot of the problems go away.  To that end, here are the 5-year looking forward aging curves for Win Shares.  Thanks to Studes for publishing the database.  Here’s how to read the chart:
All players since 1946.

PosClass: pitcher (P) or nonpitcher (nonP)
Age:
WinSharesClass: 0-4, 5-9, 10-14, 15-19, 20+
n: number of players in class
startWS: win shares at Age
avgWS: average win shares over the next 5 years after Age
rate: avgWS / startWS

So, there were 59 nonpitchers at age 22 with at least 20 win shares, for an average win shares of 25.1.  In the 5 subsequent years (ages 23-27), they averaged 23.4 win shares, retaining 93% of the win shares at age 22.

You will see two sheets: one is the data, aggregated, and the other is a subset of that data in an easy-to-use table.