Blizzard made some changes to their internal player MMR rankings. They've talked about it in their Ranked Play Revamp blog post, and their Unranked Draft Mode and More! blog post.

Since HOTS Logs MMR is overall trying to estimate Blizzard's internal MMR, we'll also follow along with these changes.

The general idea of these changes is that everyone keeps their current place on the Leaderboard, but the space between players is reduced, and each player's MMR uncertainty is increased.

This means it will temporarily be easier for players to ascend or descend the ladder.