The correlation between xpm and Win Rate is 0.81. The more xpm, the more Win Rate, and vice versa. But some values are higher than expected, some are lower. Efficiency is a difference between the value of Win Rate depending on xpm (blue dots) with respect to the expected value (red line).
Efficiency
Stormcrafter 0.0473
Book Of The Dead 0.0402
Telescope 0.0369
Arcanist'S Armor 0.0328
Ceremonial Robe 0.0311
Arcane Ring 0.0265
Bullwhip 0.0263
Seeds Of Serenity 0.0190
Timeless Relic 0.0177
Spell Prism 0.0173
Quickening Charm 0.0170
Trusty Shovel 0.0163
Ring Of Aquila 0.0146
Dandelion Amulet 0.0130
Psychic Headband 0.0126
Giant'S Ring 0.0122
Eye Of The Vizier 0.0108
Ascetic'S Cap 0.0099
Seer Stone 0.0079
Force Boots 0.0066
Gossamer Cape 0.0063
Mirror Shield 0.0050
Cloak Of Flames 0.0036
Defiant Shell 0.0028
Occult Bracelet 0.0017
Fairy'S Trinket -0.0016
Martyr'S Plate -0.0027
Dragon Scale -0.0027
Faded Broach -0.0036
Stygian Desolator -0.0051
Pupil'S Gift -0.0058
Fallen Sky -0.0063
Apex -0.0073
Havoc Hammer -0.0074
Mind Breaker -0.0081
Tumbler'S Toy -0.0104
Grove Bow -0.0115
Penta-Edged Sword -0.0117
Enchanted Quiver -0.0119
Pirate Hat -0.0122
Book Of Shadows -0.0138
Lance Of Pursuit -0.0140
Pig Pole -0.0147
Ninja Gear -0.0158
Paladin Sword -0.0159
Ex Machina -0.0171
Vampire Fangs -0.0189
Titan Sliver -0.0192
Ogre Seal Totem -0.0196
Philosopher'S Stone -0.0203
Spark Of Courage -0.0208
Trickster Cloak -0.0209
Vambrace -0.0215
Elven Tunic -0.0252
Broom Handle -0.0280
Duelist Gloves -0.0417