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Hypotheses
1.There will be a core of developers who control the code base and create >=80% of new functionality.  If coordination is ad hoc, this group will be <=15 people.
2.If size of project requires a core >15, there will need to be explicit development processes, code ownership, required inspections
3.A group larger by an order of magnitude will repair defects, and a group larger by another order of magnitude will report bugs