WHULorigan
Emperor Mongoose
Then who does the count? The individual planets or the IISS? If it is the individual planets, does that mean that planetary or balkanized governments decide who is a citizen of the Imperium and who is not or does the Imperial government determine that? All of the books say that the UWP of a world is determined by the IISS.
But I think the point is the population code is not a matter of "Imperial Citizenship", it is a matter of "permanent residency on-world". If the world is an Imperial member-world, then its permanent resident population are by definition "Imperial Citizens", being that they are citizens of the world.
Even if there is an odd cultural situation in which only certain "classes" or "castes" of people within a particular population of a world are considered "citizens" of that world by the local culture or government (say like Roman Citizenship within the Roman Republic and Empire prior to Emperor Caracalla - it was a privileged social position) - that would not necessarily have a bearing on any kind of concept of "Imperial Citizenship", or the IISS records, as the Imperium is largely indifferent to local laws, customs, and culture. And the IISS records in the Survey certainly extend to worlds well outside the Imperium, where nobody is an Imperial Citizen. And I would certainly think that the IISS does not have its "count" or "census" dictated to it by a member-world government.
So the intention certainly seems to be to record a census of the number of permanent or long-term on-world residents. If it does not, then the reason for that should first be determined as to whether it is simply an authorial change to the canonical data (as aggravating as that may be), and if it is not harmonizable, to make a fiat decision to go with one or the other dataset (and no I don't like that solution). Otherwise, the reason is to be found in-setting (and I unfortunately do not have a good explanation at the moment).
Perhaps, going off of my statement above about the IISS "not having its "count" or "census" dictated to it by a member-world government": is it possible (considering how the IISS has been used historically by the Imperial Government for Trade, Control, and Intelligence purposes, that the IISS has deliberately reported the figures the way they have for a political or punitive reason of some sort?