And one more:
How about approx. population density/sapient life occurrence frequency/percentage of races successfully achieved spaceflight without rendering themselves extinct etc. of Associated Worlds?
Well, now. If you were to compare the number of species around the place in the Worlds to the total number of star systems connected, what you would get is something on the order of one sophont species per 40 to 60 star systems. Once you eliminated all the digisapiences, neogens, post-technological speciation, polytaxic species, nomads, and suchlike that complexify the issue, anyway. (95% to 98% of those haven’t rendered themselves extinct; it’s rare that people manage to screw up that completely, especially once starflight is available, but the ones that have are rather prominent in the news and history books for obvious reasons. Maybe 25% of them had interplanetary flight/in-system development when contacted.)
Of course, that’s completely non-representative.
The Far Horizon Probes that Ring Dynamics and the Exploratory Service use to decide where and when to expand the stargate plexus are programmed with certain biases, mostly towards interesting things. Like, say, the blue-white giant star Leytra in the middle of the Ringstars constellation, or the Eye-of-Night black hole, both unique features. But also, always, the signs of intelligent life (which, of course, further biases it towards species advanced enough to produce radio signals or other features observable across the light-years).
So that’s not the number of species spread over 10,000 systems, because the 10,000 systems connected to the Worlds are spread across a volume of space – an oblate spheroid with axes roughly 3,300 ly by 4,100 ly by 2,000 ly – that contains maybe 100,000,000 star systems. So, the prevalence of sophont life is more like 1 per 400,000 star systems in the aggregate. (I’m erring to the high end, here, since pre-technological star systems are effectively invisible except at close range.)
Local population density varies widely throughout the Worlds, of course, just like it does in the greater Galaxy. (Some bubbles are life-rich, some are less so, some have been scoured entirely clean of life by, say, supernovae and gamma-ray bursters. Plus, of course, the inner and outer thirds of the galaxy tend to be life-poor compared to the central band: the former because of the high radiation levels near the galactic core, and the latter because of the lack of necessary elements.) But that’s the average, and the Worlds bubble is… average, maybe a little on the high side, by galactic standards.