This page explains how Robert D. Halladay (USATT# 6380)'s rating went from 1354 to 1353 at the Portsmouth Invitational held on - 23 May 1999. The links below take you to pages that describe various aspects of the rating processor.

The rating processor goes through 4 passes in order. The links take you to pages that provide detailed explanations of the calculations during each of the 4 passes.