The correlation between gpm and Tower Damage is 0.74. The more gpm, the more Tower Damage, and vice versa. But some values are higher than expected, some are lower. Efficiency is a difference between the value of Tower Damage depending on gpm (blue dots) with respect to the expected value (red line).
Efficiency
Lone Druid 167.8332
Visage 111.3866
Lycan 96.7758
Broodmother 92.2297
Clinkz 85.7885
Troll Warlord 79.4980
Morphling 59.7736
Meepo 59.5777
Shadow Fiend 59.1446
Terrorblade 57.9959
Chen 53.8082
Shadow Shaman 52.2747
Pugna 46.8565
Luna 43.8403
Huskar 42.1127
Dragon Knight 41.4286
Abaddon 39.6187
Drow Ranger 32.9312
Lifestealer 32.4260
Weaver 31.1576
Jakiro 30.6854
Chaos Knight 26.7755
Warlock 26.5863
Marci 25.9242
Io 25.7999
Wraith King 25.4479
Gyrocopter 25.2595
Enchantress 24.2478
Tiny 21.9594
Muerta 21.3652
Leshrac 18.8760
Brewmaster 17.4544
Juggernaut 17.2557
Viper 16.6537
Death Prophet 16.2227
Beastmaster 16.2079
Legion Commander 16.0822
Treant Protector 13.0480
Templar Assassin 12.9418
Nature's Prophet 12.6097
Windranger 12.0593
Night Stalker 11.6055
Sniper 10.7873
Slark 9.9061
Enigma 8.6429
Bane 6.2247
Tidehunter 5.9445
Vengeful Spirit 4.9616
Dark Willow 4.8688
Monkey King 4.3704
Omniknight 4.1405
Underlord 4.1396
Mirana 2.9041
Sven 2.8124
Anti-Mage 2.5045
Silencer 2.3033
Naga Siren 2.0963
Invoker 1.5690
Phantom Lancer -2.8397
Elder Titan -3.1411
Dazzle -3.8952
Shadow Demon -3.9656
Crystal Maiden -4.0957
Oracle -4.7013
Winter Wyvern -4.9043
Razor -4.9392
Snapfire -5.0181
Disruptor -5.0227
Venomancer -5.1002
Lion -7.5607
Void Spirit -7.7631
Medusa -8.5958
Grimstroke -8.9725
Phoenix -10.1498
Tusk -11.1066
Skywrath Mage -11.2542
Outworld Destroyer -11.6928
Lich -12.5341
Undying -12.7731
Techies -14.0970
Ancient Apparition -14.4259
Clockwerk -15.2077
Hoodwink -15.2240
Magnus -16.6720
Bristleback -17.4648
Centaur Warrunner -17.6508
Bloodseeker -17.7571
Rubick -17.9901
Earthshaker -18.4689
Lina -18.6033
Slardar -18.9828
Pudge -22.1230
Nyx Assassin -22.1864
Dawnbreaker -23.8711
Mars -25.6233
Earth Spirit -25.6395
Queen of Pain -28.3962
Witch Doctor -29.0400
Primal Beast -30.1498
Faceless Void -30.2256
Batrider -30.5664
Ogre Magi -30.7282
Spirit Breaker -33.8600
Keeper of the Light -35.1587
Riki -35.7277
Timbersaw -36.1926
Storm Spirit -36.7884
Puck -42.1596
Ursa -42.7521
Dark Seer -43.5247
Spectre -43.9455
Arc Warden -44.4016
Kunkka -44.9530
Phantom Assassin -46.4352
Bounty Hunter -47.9887
Pangolier -52.4821
Sand King -53.2911
Ember Spirit -53.9223
Axe -55.9928
Zeus -61.1047
Alchemist -75.5025
Necrophos -75.8219
Doom -89.7811
Tinker -96.7964