I really have a bad memory, so I am looking at Ian as a reliable and trustworthy source to see if he remembers and era of slaughter, mayhem and genocide in the early history of Colonia.
You've been there even longer than I have, so if it was before October 3302 I might not have noticed.
Early history? The biggest public exodus of Colonia inhabitants was probably after the announcement of the Colonia Expansion Initiative, from those explorers who disliked the idea of any sort of PMF interaction or BGS activity within Colonia - and for whom the establishment of the Colonia Council as a non-Jaques faction had already been a worrying step in the wrong direction from their point of view.
Then I guess you've got the disintegration of the original CCN [1] under the dual pressures of the CEI factions not wishing to work with it politically and a certain second-wave CEI faction moving straight to opening fire on it. Probably quite a few more left at that point. That would certainly fall under the "slaughter and mayhem" bit, since it turns out that high-end PvP ships flown by some of the best pilots in the galaxy cannot effectively be fended off by mediocre pilots in Jaques' finest D-rated Vipers.
Obviously there's lots of churn as people come and go, especially as the region became a more useful base for explorers, but that's not systematic in any way.
After that? Generally the population/activity trend has been slowly upwards, but of course that could hide the disappearance of a large number of CMDRs from the region nevertheless.
Of course, early history isn't relevant to anything Loren's Reapers may or may not have done since their arrival in the region from spring 3305 onwards, so this is just for historical interest. Of course, quite a few of the political pressures driving this current conflict were indeed set in those unstable times of early 3303 ... but Senator Loren still being alive then, and the Nameless not yet having established Carcosa, those presumably aren't what Tebori is talking about.
There are of course lessons for from those times to consider about who Colonia's inhabitants actually are, especially in why the original CCN was so fatally wrong about it. But since this thread appears to be at the throwing chairs stage of the bar brawl, that might be a conversation for another time.
[1] Very very different to the faction and group of the same name nowadays, and nothing I'm saying here should be taken to be relevant to the current organisation.