I just got a common artifact "Army Camp Boost" which gives 10% passive army camp bonus.
Army production: Without the artifact -- 31.7285 K/sec With the artifact -- 33.0235 K/sec Difference of -- 1.295 K/sec = 4.08% Real 10% would be +3.17285 K/sec (no shocker, it's simple math)
Now assuming that the artifact +10% bonus is calculated from the base value instead of the cumulative value including all bonuses which includes mobile +20% army bonus, the math becomes:
Without the artifact -- 31.7285 K/sec Without artifact, without +20% mobile bonus -- 26.4404 K/sec Real 10% of this base would be +2.6440 K/sec, which is still much higher than the actual bonus provided of 1.295
Yea that would account for it. I have +100% AP upgrades for Army Camps, and 3 of the +15% army camp Techs ... so the amount I'm receiving is ~4% ... so *2+3*15% would explain this.
Unfortunate and disappointing ... b/c as it is now I could pick up a +100% artifact and it would only actually increase my army income for ~40% instead of the expected 100%.
Similar to the "Hospitals before Joint Strike" discussion, the math always seems to be rigged to give us the least benefit.
I suppose at least the description aligns with this though ... "Increases armies produced by army camps by 10%" ... so technically it is doing what it says by increasing the armies actually _produced_ by the army camps by an additional 10%.