tl;dr version: developers need a separate squish formula for kyber 1 and possibly kyber 2, and a corrective positive squish this month. Analysis of the squish devs are using explains why!
Problem: Kyber1 is down to 6% of kyber, and 1.1% of player base. This has happened through squish.
Discussion and background:
Currently, squish is being applied as a linear relationship of squish value to skill rating across each league. This works for most of the player base, since there is free flow of players from above and from below the division such that over the month, the players "spread" from the middle of each league out to the edges.
However, it fails in kyber, since kyber 1 is at the edge of the player base. At the top of kyber, players can only come from the bottom, they can't be brought in from "the league above" since that doesn't exist.
Because of this unique property of kyber 1, we shouldn't push players out of kyber 1 through the squish. Over all, skill rating points won and lost in combat is zero sum; any skill rating points won by one player are lost by another. In the context of kyber 1, that means each player who enters kyber 1 does so by pushing someone else out. So kyber1 can't grow over the course of the month the way the other league "div 1" can.
In fact, natural movement of skill rating in kyber 1 would be net negative even without squish, since anyone in kyber 1 who forgets to register is pushed down in skill rating, while combat again will be net neutral.
I would like devs to carefully consider this! For the next month or two, we need a positive rather than negative squish to get kyber1 back to 10% of kyber. After that, rather than a linear formula for skill rating to squish across all of kyber, you will want to apply a separate formula for kyber 1 - while I recognize the need to reduce the range of rating variation within kyber1, that has to be tempered by consideration of how to maintain the size of the division.
Thank you for coming to my talk!