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If you're low on math this concept captures the point quite well i think (business is easy to model as a network): https://en.wikipedia.org/wiki/Clustering_coefficient#Local_clustering_coefficient …
Ehhh..."teaching birds to fly" Your point though is why every product which can be shipped reasonably easily clusters, i.e. a town in China for socks, for bras, for toilets, etc. Concrete on the other hand needs a plant in every significant population center, USA and China.
It's not really teaching, it's illustration. Anyway, not that important.
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