Does the order of Portal Shields matter?

Question

As Ingress Field Guide(along with many other Ingress game guides) states that each portal shield placed after the first one will have diminished effect.

Portal Shield:

A type of MOD that can be installed on a Portal to increase its defense against attacks. You can deploy up to 4 shields per portal, but each shield has diminished effect after the first one.

What I wonder is, ordering of the shields after the first one is differed or not. I mean, Placing

VR, R, C, C *

and

VR, C, C, R *

are differed in effect?

---

* VR: Very Rare, 
  R: Rare, 
  C: Common

Answer 1

A single Portal shield makes attacks 6% / 8% / 10% less effective. So if an attack without shields does 100% damage, with one VR shield the damage is 90%, and with two VR shields it'd be 81% (0.9*0.9). So four VR shields would reduce damage to 66% (0.9^4).

The effect is "diminished" because if you would simply add up the protection values, you'd end up with 60%.

Thus, since multiplication is commutative, order doesn't matter.