Chess.com ratings

I lost against a player with worse rating (about 100 less than me) and lost 10 points. After that, I've won against a player with better rating (almost 200 more than me) and won only 11 points.

Here is the last 3 results table:

What could be the explanation?

Thanks.

Blame Professor Glicko and his rating system.  You have to be a whiz at calculus to fully understand it, but here are some previous threads:

http://www.chess.com/forum/search?keyword=Glicko+RD

And now I got 8 points for winning against an adversary with a rating closer to mine...

Hopefully chess.com algorithms don't have bugs nor glitches and are also a whiz at calculus...

Rating changes are based on a number of factors, not just your rating compared to your opponent's rating.

The system that chess.com uses, which baddogno referenced above, also includes something called RD, which is really just a measure of how accurate your rating is (lower numbers indicate a more accurate rating).

Perform as your rating indicates (losing against higher-rateds, winning against lower-rateds, and drawing against equal-rateds), and your RD goes down - it is considered accurate.  Your rating won't change as much anymore.

Perform in a way contrary than you would expect for your rating, and your RD goes up - your rating is considered inaccurate, and your rating will jump around a lot more until your performance more closely matches your rating.

Additionally, your opponent's RD is also taken into account when calculating new ratings.  If your opponent's RD is high (rating is inaccurate), then your rating won't change as much.

Finally, your RD will slowly climb up while you aren't completing games.  The longer the time is between games, the more likely your rating is going to be inaccurate.

As ominpaul says, it's not just your rating compared to your opponent's.

The more often you play, the less your rating will change from game to game.

In my last game I beat a player 130 points over me. I gained 42 points and he lost 16. But he plays a lot and I've only played 20 games here in a year and a half.

OK. I will take a deeper look into it, but it seems strange that decreasing seems easier than increasing.

That's just because of the particular players you played and the order in which you played them.  If you notice ipcress12's situation above, his rating increased a lot more than his opponent's was decreased.  ipcress12's rating was considered inaccurate, so his rating changed by a lot.  His opponent's rating was considered accurate, so his opponent's rating didn't change very much.

I remember one opponent I played.  His rating went up over 400 pts after he beat me, while mine went down only a few points.  Then again, I complete games very regularly and have a very accurate rating while my opponent at that time had never completed a game on this site, so his initial 1200 rating was naturally extremely inaccurate.