This page explains how Bill Lum (USATT# 55787)'s rating went from 1668 to 1639 at the 2005 US Nationals Championship held on - 17 Dec 2005. 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.