This page explains how Michael Halliday (USATT# 12560)'s rating went from 1621 to 1607 at the NY Open Circuit - Rochester Gi held on - 28 Feb 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.