The correlation between xpm and Win Rate is 0.71. 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
Holy Locket 0.1366
Boots Of Bearing 0.1345
Guardian Greaves 0.1290
Vladmir'S Offering 0.1016
Assault Cuirass 0.0827
Overwhelming Blink 0.0766
Aeon Disk 0.0763
Moon Shard 0.0727
Pavise 0.0724
Refresher Orb 0.0693
Wind Waker 0.0679
Solar Crest 0.0673
Heart Of Tarrasque 0.0652
Meteor Hammer 0.0648
Octarine Core 0.0646
Pipe Of Insight 0.0558
Helm Of The Overlord 0.0552
Arcane Blink 0.0542
Aether Lens 0.0507
Lotus Orb 0.0495
Revenant'S Brooch 0.0484
Glimmer Cape 0.0475
Shiva'S Guard 0.0470
Yasha And Kaya 0.0456
Boots Of Travel 0.0435
Veil Of Discord 0.0404
Drum Of Endurance 0.0375
Aghanim'S Scepter 0.0365
Spirit Vessel 0.0353
Crimson Guard 0.0343
Rod Of Atos 0.0325
Scythe Of Vyse 0.0303
Boots Of Travel 2 0.0285
Dagon (5) 0.0274
Force Staff 0.0273
Aghanim'S Shard 0.0272
Bloodthorn 0.0271
Aghanim'S Blessing 0.0229
Phylactery 0.0224
Harpoon 0.0204
Butterfly 0.0184
Linken'S Sphere 0.0137
Arcane Boots 0.0126
Tranquil Boots 0.0120
Eul'S Scepter Of Divinity 0.0120
Ethereal Blade 0.0102
Disperser 0.0099
Bloodstone 0.0098
Satanic 0.0075
Abyssal Blade 0.0069
Eye Of Skadi 0.0064
Gleipnir 0.0046
Mekansm 0.0045
Eternal Shroud 0.0040
Kaya And Sange 0.0030
Swift Blink 0.0020
Dagon (4) -0.0038
Daedalus -0.0047
Blink Dagger -0.0054
Magic Wand -0.0071
Hurricane Pike -0.0082
Radiance -0.0098
Sange And Yasha -0.0144
Heaven'S Halberd -0.0154
Null Talisman -0.0194
Urn Of Shadows -0.0279
Bracer -0.0288
Mjollnir -0.0288
Armlet Of Mordiggian -0.0303
Nullifier -0.0305
Dagon (3) -0.0306
Desolator -0.0314
Soul Ring -0.0325
Witch Blade -0.0342
Blade Mail -0.0344
Orchid Malevolence -0.0379
Phase Boots -0.0450
Silver Edge -0.0469
Manta Style -0.0474
Medallion Of Courage -0.0487
Orb Of Corrosion -0.0516
Dagon (2) -0.0519
Skull Basher -0.0537
Dagon -0.0547
Black King Bar -0.0597
Vanguard -0.0610
Helm Of The Dominator -0.0630
Power Treads -0.0670
Mage Slayer -0.0687
Monkey King Bar -0.0714
Wraith Band -0.0729
Diffusal Blade -0.0738
Hand Of Midas -0.0738
Falcon Blade -0.0778
Bottle -0.0783
Echo Sabre -0.0835
Dragon Lance -0.0867
Mask Of Madness -0.0969
Battle Fury -0.1047
Shadow Blade -0.1109
Crystalys -0.1306
Maelstrom -0.1497