In regards to how many worlds should be within a certain jump distance of Earth, my (finally existing!) game has Jump space be an effectively 2d dimension that does not match the physical universe, so systems 1 jump away can be barely detectable by telescope in real space. Incidentally, this also uses a variant of Jeff's "Color of Jumpspace" articles, with a partially visible jump dimension - you can see nearby systems when you jump (with a partially steerable jump bubble), but you don't know what's in them until you get there (computer survey that suckers! Scouts, ready to roll!).

The end result: I don't have to care about real world astrography, or 3d space maps.

In regards to everything else, propaganda (11,000 worlds may include some dustballs), frequency of surveys (it was pop 3... 50 years ago), colonization initiatives to have boots on the ground in what would otherwise be unsettled systems, and the equivalent of rural migration to cities (lo pop planets loosing younguns to hi pop glitter and work opportunities).