[statnet_help] fragmented bipartite network...

[Martina Morris]

Hi Harald,

I'm looking for some clarification here, which I think Tom Kraft might also
have wondered about.

You say:

Our research focuses on tie formation and elite cohesion, specifically
examining interlocking directorates and kinship relations. The dependent
bipartite business network comprises 6,902 individuals and 5,178
companies, exhibiting
sparsity (density = 0.00012) and fragmentation with 4,455 components,
including 3,850 isolates in the first mode (persons)

For a bipartite network ties are allowed only between modes (persons,
companies), not within.  It's clear how interlocking directorates would
meet that criteria.  But kinship relations would be among persons, so
within-mode, not between, and this would not be a bipartite network.

Is the model you've sent us for the interlocking directorships only?  And
by isolates in the person mode, do you mean persons who are not affiliated
with any of the companies?  If so, then it's a bit odd to include them in
the bipartite network.

I'm wondering if this problem is better posed as a multilevel network (not
my area of expertise).

thanks,
Martina


On Thu, Nov 30, 2023 at 4:33 PM Carter T. Butts <buttsc at uci.edu> wrote:


> Hi, Harald -

>

> Coexistence of large complex components does not generally occur unless

> something drives the fragmentation, and this is what your models are

> telling you: the terms you are currently using do not include the forces

> that are sufficient to reproduce your component size distribution.  That

> means that you need to think about why your network is split into

> fragments, and include terms that capture the relevant social forces.

> Thinking about likely mechanisms is step zero, so do that before anything

> else!  Guided by your substantive knowledge of what is likely going on, you

> will next (as others have said) want to look at covariate effects relating

> to differential mixing, since those are your most obvious and most

> important sources of heterogeneity.  If you find that there is still more

> fragmentation that can be explained by other means, you may need to

> consider model terms relating directly to component count or size.  These

> are still somewhat experimental, and are currently sequestered in an add-on

> package called ergm.components (https://github.com/statnet/ergm.components

> <https://urldefense.com/v3/__https://github.com/statnet/ergm.components__;!!K-Hz7m0Vt54!iKts-XLv39sY0gvmpW6MWLIxNMCNKjKQKOhJszIbp3PIy_J5mdLCs0MytfHsBu-cjnQjk997tCRX0MMs6LDW$>).

> However, this package can be installed from github (see the github page),

> and the terms will work automagically with ergm() and friends once the

> package is loaded.  Depending on your situation, you may need or want to

> examine the components() or compsizesum() terms, both of which are

> documented within the package.

>

> Hope that helps,

>

> -Carter

> On 11/30/23 9:58 AM, Harald Waxenecker wrote:

>

> Dear ‘statnet community’,

>

>

>

> Our research focuses on tie formation and elite cohesion, specifically

> examining interlocking directorates and kinship relations. The dependent

> bipartite business network comprises 6,902 individuals and 5,178 companies,

> exhibiting sparsity (density = 0.00012) and fragmentation with 4,455

> components, including 3,850 isolates in the first mode (persons). The

> attached documents contain descriptives and the component size distribution

> from the observed network.

>

>

>

> The fragmented structure is important, as other network layers, like

> kinship relations, are expected to contribute to the cohesion of this

> business network. We apply ERGM to model these processes, but we struggle

> to capture the fragmented structure of the observed network. The component

> size distribution of the simulated network differs significantly. In

> addition, the goodness-of-fit (GOF) for k-stars (in both modes) and

> geodesic distances (Inf) shows significant results. All these results are

> also attached.

>

>

>

> We've explored various options, including constraints, MCMC propositions,

> and simulated annealing, but haven't achieved success. Please, we would

> like to ask for your help to improve our model. Thank you!

>

>

>

> Kind regards,

>

> Harald

>

>

>

>

>

>

>

> ---

>

>

>

> *Harald Waxenecker *

>

> *Masaryk University | Faculty of social studies*

> Department of Environment Studies

> A: Jostova 10 | 602 00 Brno | Czech Republic

> E: waxenecker at fss.muni.cz

>

>

>

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