User:Lithistman/Harkness system

The Harkness System is a chess rating system invented by Kenneth Harkness, who published it in 1956. It was used by the United States Chess Federation, as well as some other organizations, from 1950 to 1960.

Format
When a player competes in a tournament, the average rating of his competition is calculated. If the player scores 50% he receives the average competition rating as his performance rating. If he scores more than 50% his new rating is the competition average plus 10 points for each percentage point above 50. If he scores less than 50% his new rating is the competition average minus 10 points for each percentage point below 50.

Example
A player with a rating of 1600 plays in an eleven-round tournament and scores 2½-8½ (22.7%) against competition with an average rating of 1850. This is 27.3% below 50%, so his new rating is 1850 - 10 × 27.3 = 1577.