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I have a question on a centrality index - don't know if I just invented
a new one, or whether I have reinvented an old wheel of unknown quality...
In my PhD thesis, I play around with intl trade flow matrices, i.e.
directional valued matrices with quite large value-spans between
different actors. While primarily looking at the role-structures
(conceptualized through regular equivalence), I am also interested in
looking at the relationship between different indices of "centrality"
and more mainstream (actor-based) attributes on economic well-being.
As I am especially interested in the number of trading partners each
country has, both with regards to exports and imports, I have
experimented with a simple heuristic for counting the number of
significant trading partners for each country. However, I don't know if
this same procedure has been done before - and if so, what this type of
degree-style centrality index is called.
How I calculate the number of partners an actor has:
First, I look at the "outflow profile", i.e. the row-vector for each
actor. Each outflow that is larger than 0.5 percent of the total outflow
is included in my count. I.e., if an actor has a total outdegree of
1000, I count the number of outflows which are higher than 5. Secondly,
I do the same thing for the "inflow profile", i.e. by looking at the
col-vector for each actor. Similarly, I count all inflows that are above
0.5 percent of the total inflows to the actor. Then I calculate total
number of partners by adding the number of inbound and outbound
partners. (The 0.5 percent "significance threshold" is of course
arbitrary). (As the same partner actor could be counted twice - inbound
as well as outbound - one could choose to only count each trading
What I thus try to do is to only count the number of "significant"
partners, where significance is defined on a per-actor basis. The
resulting index is very interesting for my data-set: I find a
statistical association between total number of trading partners
(weighted to total trade flows) and economic well-being.
What is this centrality index called (as I assume the above has been
Carl Nordlund, BA, PhD student
Human Ecology Division, Lund university
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