As you can see in the post that followed, we repeated the test with these two avatars using the same number of hits with the same weapon with the same efficiency and also encountered a difference in return rate there, however, lower, meaning that that difference was based entirely on Looter Profession while the other difference was based on both Looter Profession as well as Efficiency.
There is something noteworthy to mention here though, since it is possible the test could have been skewed in the possibility that Efficiency's effect on loot return is non-linear, however, given that the first test yielded a
~3.3% difference and the second test yielded a
~1.14% difference we can see that:
3.3-1.14 = 2.16
14% efficiency = roughly
1% return rate if linear
2.16*14= 30.24
difference between mod lr32 and imk2 in efficiency =
~30.2%
This pretty much proves that the Efficiency number does exactly what they said it does without any trickery and follows a linear scaling.
Of course, the numbers are slightly off, but that's to be expected since they weren't 1 million shrapnel loots, and Efficiency only goes to one decimal point.
I think this info is very useful, and I think it would be great to further test the difference in return rate this way between avatars with various Looter levels to see exactly what kind of impact on return rate it can have and at what kind of level the impact starts to lessen.