Ring equipment system

This system should be adaptable to any fantasy-themed game.

A human has ten fingers, so why should one be limited to one or two powerful magic rings? Shouldn't one be able to wear a ring on each finger? And why should one wear only one ring per finger? One can easily wear more than one on each.

The reason is game balance. Allowing so many rings would mean that they would have to be pretty weak compared to other equipment, otherwise they would outclass everything else.

So I came up with a system which allows one to wear as many rings as one likes, but many rings disturb each other, so that they don't give their full effect. So the more rings you are wearing, the less effect does each single ring have. My formula is:

Efficiency per ring = 100% * (0.9 ^ (number of rings - 1))

Coincidentally, the effect of this formula is that adding more rings after 10 results in a reduction of the overall stat bonus instead of an increase, so there is no reason to do so. Exhausting this maximum is only advisable when all rings are of equal power. Otherwise the weak rings will drag the strong ones down.

Number of rings	Efficiency of each ring	Sum of effect of all rings
1	100%	1
2	90%	1.8
3	81%	2.43
4	73%	2.92
5	66%	3.28
6	59%	3.54
7	53%	3.72
8	48%	3.83
9	43%	3.87
10	39%	3.87

In my mage-war system - should I decide to use it - rings should only increase basic attributes and elemental protection. For tactical reasons any offensive elemental specialization should be visible on the character.