## Computing a company's shareholders ownership percentage

I have a graph that contains two types of nodes: Companies and Persons.

A Company node has a list of edges that represent Shareholders. A Shareholder has a percentage of shares and is either a Company or a Person. A Person node is always a leaf.

Here's an example:

```
CompanyA has 50% of CompanyB's shares
UserA has 50% of CompanyA's shares
UserB has 50% of CompanyB's shares
CompanyB has 50% of CompanyA's shares
```

*The arrows could be reversed, depending on whether they represent shares or owners*

Who in truth owns CompanyA and with what percentage. In this example, we should get that UserA owns 66.66% of CompanyA and UserB owns 33.33% of CompanyB.

This can be computed using a Transition Matrix and multiplying it by itself multiple times, like this.

Sadly, this is an estimate and requires quite a lot of iterations to get a very precise one. I suspect that there's a way to get a exact answer. I've looked at eigenvalues but I think my maths are failing me. In terms of matrices, I think I'm looking for the stable distribution of a transition matrix (or Markov Chain).

Perhaps I'm overcomplicating this? I feel like there should be a way to get this result without resolving to matrices and with a recursive algorithm. Especially considering that the graph contains a lot of leaves and that I am only interested in the shareholders of a single company (the "root" of the graph).

I will implement the final solution in Java. Third party libraries can be used.

Thanks!

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## Answers to Computing a company's shareholders ownership percentage ( 1 )

I assume that the labeling of your matrix is more or less like so

where cA/B denotes Company A/B while uA/B stands for User A/B.

Let's denote this matrix as

`A`

. Then the expression`(1, 0, 0, 0).A`

gives us the immediate "distribution of resources" after "investing" 1 "unit" into Company A. In this case the result is indeed`(0, 0.5, 0.5, 0)`

, i.e., Company B gets 50% and User A gets 50% as well. However, the resources attributed to Company B "propagate" further, so in order to find the "equilibrium" distribution, we need to calculatein the limit of

`n`

going to infinity. In terms of the left eigenvectors, the original matrix`A`

can be rewritten (assuming that it is diagonalizable) as`A=Inverse[P].w.P`

, where`w`

is a diagonal matrix containing the eigenvalues. Then one hasIn this particular case, the eigenvalues are

`1, 1, 0.5, -0.5`

so when`n`

goes to infinity, only the eigenvalue`1`

survive(s). Thus the limit of`w^n`

is`DiagonalMatrix[{1,1,0,0}]`

. The final result can be therefore written aswhich yields

Finally, the eigenvectors corresponding to the eigenvalue 1 are

`(0, 0, 1, 0)`

and`(0, 0, 0, 1)`

. The meaning of this is that if one "invests" 1 unit of resources into User A/B, the corresponding user "keeps everything" and nothing propagates further, i.e., an equilibrium has been already reached. The eigenvalue is then doubly degenerate since there are two Users (leaves).