Just to add:
When I was a member of The Peoples Club a member decided to try and reverse engineer the formula for the effect on an average of beating a higher ranked player. This member is still in that club, is very much into Math and is quite good at it, he worked out that the reduction in your average was quite marked (he did come out with a number but I cannot remember what it was, Alosso's 0.7 doesn't sound unreasonable), but he also noted that the reduction in your average was reduced (i.e. the effect got less) over the next 25 rounds.
He was careful only to beat an opponent once during this time to enable him to track the effect because as he said, if you were to beat someone else in that time you would have two (or more) different effects often countering each other, if you then add in the 'normal' effect of a stroke play game (especially after saturation), then it become near impossible to track.
Finally, this was quite a while ago and things do change, for example I have since heard people give the opinion that this effect is only applied now if there is money at stake in the game and that this was brought in to counter those players who were getting a higher tiered 'friend' to deliberately throw a match so they could tier up earlier, (although for the life of me I cannot work out why they would want to do that, the legend tier is challenging enough with top level kit, I wouldn't want to think about it with beginner kit).