Gav opened up with his thoughts on the Craftworld Eldar after covering them in Black Library novels.
via Eldargal and Warseer
Take it away Mr. Thorpe:
“My interpretation is that the largest craftworlds would have a population in the low millions and the smaller vessels in the thousands. A craftworld the size of Alaitoc has a living space larger than a typical Earth continent, with the majority of the population concentrated in habitat domes and a scattering of others across the ‘wilderness’ zones. This would equate to a small present-day city spread across an environment the size of North America. Perhaps the Path series doesn’t quite convey how massive some of the domes are and how much of a craftworld is virtually unihabited – like most conflicts, the majority of the human invasion is focussed on the populated areas. Hopefully the battle scenes in the forest dome, involving huge columns of tanks with flyers and titans in support, demonstrates that each dome could be considered a separate combat zone, each the equivalent of a country to be invaded and conquered.
These numbers are higher than those in the old quotes for the simple reason that craftworlds, at least the major ones, are considered to be on a par with many human worlds in terms of their military potential and the smaller numbers just don’t hold up to this. However, tens of millions of eldar seem to go against the whole point of them being a dying, numerically-challenged race, so a few million seems a good compromise.
With every eldar potentially able to serve as a guardian or on the ships, and the infinity circuit and advanced technologies allowing for a very small supply-side, mobilisation of nearly one hundred per cent of the population might be possible. Measured against this is the massivel labour-orientated Imperial war machine that can lay claims to million-strong armies but only when supported by tens of millions, perhaps billions of workers.
In the context of a the galactic power struggle, the Eldar craftworlds’ greatest strength lies in the difficulty of an enemy mustering enough forces in one place. The Imperium can lay claim to countless billions of warriors, but getting them to a war zone relies on limited ship capacity, and an even more limited number of Navigators. These are not issues for the Eldar hosts, which can coordinate and travel with a flexibility impossible for orks or humans to match, ensuring that their numerical inferiority is easily offset by their ability to concentrate their force where it is most effective.”
I’ll leave it up to you to delve through all the other fiction and try to determine the overall population makeup of the Eldar race amongst the Craftworlders, Dark Eldar, and Exodites. Very interesting stuff indeed. More discussion in the Lounge here.