iCEBREAKER, you are wasting my time. If you can get anyone credible here to explain to your side, I might be prompted to respond further.
What explanation is necessary? Just look at the pie chart. It shows a beautiful example of Nash Equilibrium.
And look who I've been quoting. Cypherdoc is extremely credible (not that your appeal to authority is valid, but I'll patronize you).
Which government has "made it very costly" to run a pool? Even if one did, that still wouldn't be an example of an externality.
I don't think that chart really gives us much information at all other than an estimate of how much hashing these pools have chosen to show publicly.