# Calculating the Shapley value in a weighted voting game.

Given a special case of WVG (Weighted Voting Game) of $a$ 1s and $b$ 2s and a quota q, $[q:1,1,1,1..1,2,2,..2]$. I need help with calculating the Shapley value of a player with a weight of $2$ and a player with a weight of $1$ as a function of $a$,$b$ and $q$.

I know how to calculate the Shapely value in general, but I would like to get a simple closed form for the result. I tried to think about what happens if there are only players with weights of $1$ (simple scenario $a=2k-1,b=0,q=k$ I think you will agree that $\phi_{1}(v)=\frac{1}{a}=\frac{1}{2k-1}$. the simple calculation is $\binom{2k-2}{k-1}(k-1)!(k-1)!=\frac{1}{2k-1}=\frac{1}{a}$ which is $\frac{1}{2k-1}$. The calculation for a player of weight 1 (when there are 1s and 2s) would be a sum of choosing i players of weight 1 and $\frac{q-i}{2}$ players of weight 2. similar calculation for a player of weight 2.

I tagged binomial coefficients because I thought they could be useful for counting the occurrences.

also posted here: http://math.stackexchange.com/posts/199080

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"I would like to calculate the shapely value....." Then I think you should! –  Steven Landsburg Sep 18 '12 at 21:00
This site is for research. If there's no research angle to your question, it will fit better at math.stackexchange.com –  Gerry Myerson Sep 18 '12 at 22:46
There is a research angle, it's for my MSc thesis. but maybe I should post this question there too. thanks. –  Mati Sep 19 '12 at 11:29
If you do post it there, please put a link there to this question, and put a link here to that question. We don't want duplication of effort. –  Gerry Myerson Sep 19 '12 at 12:55
You are right, Gerry. I posted the link in the question. thanks again. –  Mati Sep 19 '12 at 13:18