GreatbigHippo wrote:
I was comparing my fighters to my enemies. I noticed the 'state based damage efficiency' on mine was 68%, and on my enemies it was 98%. I was trying to figure out why, and I noticed the enemy fighters have killed 3 units, while mine have killed none. Is the damage efficiency higher if your unit kills another? Or is my damage efficiency lower because I took off from an allied airbase instead of my own? Both fighters are at 100% morale, and the upkeep is filled on mine.
Seems you didn't get a clear answer to your question, even if it was ages ago. So figured I'd revive the dead thread just to clarify it for you.
Based upon 100% moral/health:
5 stacked units have 100% efficiency.
6 stacked units have 93% efficiency.
7 stacked units have 89% efficiency.
8 stacked units have 82% efficiency.
9 stacked units have 76% efficiency.
Say you have a unit type, we'll just presume it's infantry for the sake of explanation, and that unit has, again, for the sake of explanation, 10 attack strength each;
At 5 units, the stack would do 50 damage per hour, with no strength loss.
At 6 units, the stack would do 55.8 out of 60 damage per hour, with a loss of 4.2.
At 7 units, the stack would do 62.3 out of 70 damage per hour, with a loss of 7.7, almost a full unit's strength.
At 8 units, the stack would do 65.6 out of 80 damage per hour, with a loss of 14.4, almost one and a half unit's strength.
At 9 units, the stack would do 68.4 out of 90 damage per hour, with a loss of 21.4, over two entire unit's attack strength.
And so on, and so on, and so on. There is one benefit to adding more troops, and that's overall health. If you have 10 troops, and your opponent has, say 7, you'll do more damage, if only slightly, however, you'll have an extra 3 units worth of health to go through, which will allow you to outlast your opponent in the first place. On top of that, as you lose one unit, your efficiency will increase, and the lost units damage will simply be replaced by one of the excess units you had in that stack.
Consider any troops you have inside a stack above, I'd suggest 7, as a kind of rear guard or standby reinforcements that will take the place of a previously destroyed unit, as it's destroyed, allowing your army to essentially simply grind your opponent down with sheer numbers. The old adage of cutting the head off a hydra springs to mind, that if you cut off one head, two more will take their place. A similar concept of the ancient Persian army, it was so numerous, that even if they fielded their entire army at one spot, only x amount of them could fight at any given moment. However, every time one of them died, there would be so many there, that they'd simply be replaced by another soldier who is fresh, and full of energy, whilst every time one of their opponents died, they best they could hope for was for an already exhausted soldier to now have to fight two men instead of one, making him lose his strength and resolve even faster until he finally falls from exhaustion, resulting in his death.
So there is value for those reasons alone to feel free to ignore the efficiency, and still use high numbered stacks. There is though, also another reason, and a more complicated and less encountered situation where it would be useful to have high stacks, and that's on fortifications. In my short time here, I've noticed that higher stacked units, if on fortifications, suffer the efficiency penalty for numbers at a later point (it seems to only start at 10 units, and even that is only a 2% efficiency loss), and from what I can observe, it's also at a slower loss. You can probably keep maybe 15-20 units on a level 5 fortification, and still have about a 75% efficiency I believe. Add to the fact that these fortifications make your troops take 75% less damage, in a rough estimation, I'd say as a result, those 15-20 units are probably about strong and capable, as a result of that reduction, as perhaps 30-35 units. So word to the wise, you find a high stack of units on a high level fortification... I hope you have a big army, because it's going to take a lot to win that province. It will cost you dearly.
I hope that helps even some of the more experience players 
