Why does winning lower my rank?

My overall rating (that is, the rating in the upper left) just went down from 1994 to 1978, after winning a ladder game (with 40.5 points) from an 8k opponent while I am ranked 4k. My opponent had challenged me in the context of the Site 19x19 Ladder. Should I conclude that anytime somebody challenges me in the ladder who is ranked 4k lower (or more) this simple fact will make my overall rating go down, win or lose??

Perhaps this is why. You noticed a little decrease.


In my case, the uncertainty value suddenly increases after a few games (I thought it would decrease over time)!

It makes sense to me that uncertainty increases when you beat someone stronger than you - now we don’t know how much stronger than that higher rank you might have become.