rating_changes

The following changes were made to the rating system April 28, 1997:

1. There is now a minimum "K" factor; the basic idea is that, like USCF and
FIDE, we use the formula

Rating Change = K * (W - E)

where W is 1 if you win, 0.5 if you draw, and 0 if you lose, and E is your
expected score against a particular opponent.  USCF basically uses a constant
for K; in the Glicko system, it depends on your RD and your opponent's RD. 
The change is that if we calculate a K which is less than 16, we now use 16
instead.  This means that in a match against an equally rated player, you can
always win or lose at least 8 points.

2. The rate at which RD increases when you do not play has now been slowed
down.  We had artifically increased that rate to satisfy players who wanted
larger changes from individual games.  With the new minimum K value, this is
no longer necessary.

3. Because of the slower RD increase, we now require an RD of at most 80.0 for
a user to be considered active, and to be included in the "rank" and the
"best" list.

Hersco  [4/29/97]