# Thread: Diminishing Returns - Armour

1. ## Diminishing Returns - Armour

Let's talk about armour, mitigation, and diminishing returns. First, two definitions so we're all thinking the same thing:

Mitigation - This is the amount of physical damage that your armour reduces. For example, if you have 10000 armour and are fighting a level 70 opponent, your armour gives you 48.6% mitigation, or, you take 51.4% of the damage dealt to you. For example, if the opponent hits you for 200 damage, you would take 103 points of damage. You can calculate your mitigation with this formula (assuming your oppoent is level 60 or higher - the formula is slightly different for under level 60):
Code:
```              AC
M = -----------------------
AC + (467.5L - 22167.5)```
Where level is the level of your opponent, not your own level.

Time to Live - Also called survivability. Your hitpoints and mitigation from armour combined will allow you to stay alive for a certain length of time under a given rate of damage incoming. If I have 10000 armour and 10000 hitpoints, and my opponent is level 70 and deals 200 damage per second (DPS) then:

- I have 48.6% mitigation, as above
- My mitigation means that my opponent actually is doing 102.7 damage per second to me
- My 10000 hitpoints will last for 97.4 seconds at that rate. This is my time to live
As we see, my armour and hitpoints combine together to determine how much damage I am taking, and how long I will live. We note that armour matters only for physical damage. Armour does not do anything against a fireball - that's why we have resist gear.

Also note that in the reality of the game, your opponent is likely hitting every two seconds or so, not every second. You won't actually be 102.7 damage every second. Instead, it will be more like 205.4 damage every two seconds (and you'll be actually hit for 204 or 205 damage, depending on how the game rounds that off.) This difference is a lot more relevant when something that can kill you in one or two or three hits you is hitting you! For the purpose of explaining this, we'll stick with the damage per second model to make it a bit more easy to understand.

Diminishing Returns
What are diminishing returns, anyway? Here is a definition:
In economics, diminishing returns is the short form of diminishing marginal returns. In a production system, having fixed and variable inputs, keeping the fixed inputs constant, as more of a variable input is applied, each additional unit of input yields less and less additional output. This concept is also known as the law of increasing opportunity cost or the law of diminishing returns.
In short, you have diminishing returns if, every time you add the same amount of input, you get less output. In this case, what we are looking at is adding more armour, but getting less mitigation for the armour we keep adding.

If you were to look at a graph that shows the amount of mitigation you get for the amount of armour you have, you would see that your mitigation will keep getting closer and closer to 100% but will never actually reach 100%. If you had 100,000 armour, your mitigation would still only be 85%. If you had a million armour, still only 98.35%. It's worth noting that you'll also read in http://www.tankspot.com/forums/f63/4...itigation.html that mitigation from armour has a hard cutoff at 75%. If you got enough armour to give you 75.1% mitigation, the game sill only counts you as having 75%.

We can also show that mitigation is subject to diminishing returns using a practical example:
Code:
```1) I have 5000 armour.  Against a level 70 opponent, this means I have 32.1% mitigation.
Now I will add 1000 armour, giving me 6000 armour.
Against a level 70 opponent, this means I now have 36.2% mitigation.
Adding 1000 armour increased my mitigation by 4.1%

2) I have 10000 armour.  Against a level 70 opponent, this means I have 48.6% mitigation.
Now I will add 1000 armour, giving me 11000 armour.
Against a level 70 opponent, this means I now have 51.0% mitigation.
Adding 1000 armour increased my mitigation by 2.4%

3) I have 12000 armour.  Against a level 70 opponent, this means I have 53.2% mitigation.
Now I will add 1000 armour, giving me 13000 armour.
Against a level 70 opponent, this means I now have 55.2% mitigation.
Adding 1000 armour increased my mitigation by 2.0%```
We clearly see at different levels of armour, adding 1000 armour returns less and less mitigation. This is, by definition, diminishing returns. For the more mathematically inclined, here is the general proof of this.

So Why Do People Say There Are No Diminishing Returns?
Mostly because they are talking about time to live, and are confusing labels and terminology. Look at this example:
Code:
```1) I have 5000 armour and 10000 hitpoints.
Against a level 70 opponent that deals 200 damage per second I will live for 73.6 seconds
Now I will add 1000 armour, giving me 6000 armour.
Against a level 70 opponent that deals 200 damage per second I will live for 78.4 seconds
Adding 1000 armour increased my time to live by 4.7 seconds.

2) I have 10000 armour and 10000 hitpoints.
Against a level 70 opponent that deals 200 damage per second I will live for 97.4 seconds
Now I will add 1000 armour, giving me 11000 armour.
Against a level 70 opponent that deals 200 damage per second I will live for 102.1 seconds
Adding 1000 armour increased my time to live by 4.7 seconds.

3) I have 12000 armour and 10000 hitpoints.
Against a level 70 opponent that deals 200 damage per second I will live for 106.8 seconds
Now I will add 1000 armour, giving me 13000 armour.
Against a level 70 opponent that deals 200 damage per second I will live for 111.5 seconds
Adding 1000 armour increased my time to live by 4.7 seconds.```
The 4.7 second value is rounded off. If you carry all decimal places, you see that in all three cases the increase in time to live is always 4.7359696898... seconds, matching exactly to however many decimal points you carry. This difference holds true for any given pair (X, X+1000) along the mitigation function for a fixed health value. For the mathematically inclined, the general proof of this was also here.

Well wait then, what's this? Yes, for every X amount of armour that you add, your time to live increases by the same amount, no matter how much armour you had already. This increase in time to live is indeed not subject to diminishing returns. This is where the confusion comes in. Here we plainly see that adding armour does not have a diminishing effect. But, it is the time to live function that is not subject to diminishing returns, not the mitigation function. You are talking about a different system here. Mitigation is a function of your armour and your opponent's level. Time to live is a function of your mitigation, hitpoints, and damage per second. In fact, mitigation being subject to diminishing returns is the whole reason that time to live works this way. If mitigation was not on diminishing returns, then adding X armour would change your time to live by different amounts every time.

Summary
What it all boils down to is this phrase: Mitigation is subject to diminishing returns, but armour is not. We use this one sentence to summarise both of the effects explained above. I suppose a more correct sentence might be "Mitigation is subject to diminishing returns, but survivability is not", but most people express it in the first way generally. The distinction between mitigation and armour/time to live/survivability is this:

- Mitigation is a function of your armour and your opponent's level
- Time to live is a function of your mitigation, your hitpoints, and how much damage per second you are taking
These are two different systems that are related. The second one uses the first in its calculation, and works the way it does because mitigation is subject to diminishing returns. Again we stress that this is valid against physical damage only. Once fireballs and shadowbolts begin to fly, it goes to your resistance and hitpoints instead of armour and hitpoints.
Last edited by Satrina; 10-30-2009 at 01:42 PM.

2. New Registrant
Join Date
Nov 2008
Posts
2
Thanks for this great post. Is this information valid for lvl 80? If not, do you have a revised formula? Thx!

3. This was updated/posted yesterday, you can assume this is accurate for level 80.

4. New Registrant
Join Date
Nov 2008
Posts
2
Yeah I saw it was posted yesterday but then why not use lvl 80 for running the numbers? That's why I asked.

5. Because I am lazy

6. New Registrant
Join Date
Oct 2008
Posts
1
I think your knowlegde is very helpul to a new tank thank you. After i read my first article written by you i could tank alot better

7. Tankadin
Join Date
Aug 2008
Posts
6
When dealing with mitigation it's important to note that the figure itself denotes how much damage is absorbed which is a value that player never encounters directly in the actual game. What is relevant for tanks and players in general is how much damage is left when it hits the game.

It's also important to know when dealing with percentages that if you increase mitigation from say 50% to 55% you increase mitigation by 5% points or 10%, not 5%!

However going back to the above as i said mitigation weren't all that relevant, it's what left after the mitigation have taken away part of the damage. With that i will retrify the empirical example that was posted, with what i belive to be the old lvl 60 formula.
Code:
```1) I have 5000 armour.  Against a level 70 opponent, this means I have 32.1% mitigation and I will take 67.9% of the damage it deals.
Now I will add 1000 armour, giving me 6000 armour.
Against a level 70 opponent, this means I now have 36.2% mitigation, and will only take 63,8% of the damage.
Adding 1000 armour increased my mitigation by 4.1pp, or 12,77%, reducing the damage I take by 4.1pp or 6,04%

2) I have 10000 armour.  Against a level 70 opponent, this means I have 48.6% mitigation and I will take 51.4% of the damage it deals.
Now I will add 1000 armour, giving me 11000 armour.
Against a level 70 opponent, this means I now have 51.0% mitigation, and will only take 49,0% of the damage.
Adding 1000 armour increased my mitigation by 2.4pp, or 4,94%, reducing the damage I take by 2.4pp or 4,71% of the damage it deals.

3) I have 12000 armour.  Against a level 70 opponent, this means I have 53.2% mitigation and I will take 46.8% of the damage it deals.
Now I will add 1000 armour, giving me 13000 armour.
Against a level 70 opponent, this means I now have 55.2% mitigation, and will only take 44,8% of the damage.
Adding 1000 armour increased my mitigation by 2.0pp, or 3,76%, reducing the damage I take by 2.0pp or 4,27% of the damage it deals.```
It's worth noting that it's the latter figure that's important for calculating how an armor increase will benefit you in melee.

It is indeed correct that armor does not suffer from diminishing returns when you are interested in how long you can survive without healing, in much the same way that stamina doesn't suffer from diminshing returns in the same regard.

But it is worth remembering that the relative beneficial increase you get pr point of sta or armor does diminish the more you have, unlike what used to be the case with avoidance, and what is still the case with block value.

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