fair enough.
though i have to say in the case mentioned above, it doesn't help for the 5k town to lose pop to the 10k city as any increase is negligible to the rate of growth of the city, but any loss to the town (let alone rural) will be significant, especially if it goes on for a while. in those kind of cases, it might make sense for a region to stop losing pop to cities... after dropping below some sort of threshold. (highish)..
the region my character rules neighbours 4 regions.. so it's very difficult to tell where they are legging it off to. it's a town between 2 cities and 2 rurals. all of which have lower % pop, i think. (but the cities obviously have higher pop number) it's lost at least 2k pop in the last 2 months (or since whenever the code was implemented)
