Yes, there has been very good analysis done about Demographics, unfortunately not every point has been made clear yet, but most of it is revealed...
The only points I really care for in demogrpahics is industrial producitivity ('manufacturing goods') and population. if I see someoen else is being a danger for my population rank, I also look at family size which is an indicator for population growth (food surplus basically, I don't know whether the presence of granaries comes into account as well, it should)... but then, when in republic or democracy, family size doesn't really matter anymore... now, apporval rate is way more important for pop growth
population size doesn't actually matter at all, what is important for winning the game is industrial strength, and due to wise city management I'm always ahead in thosegoods in SP games... and in most MP games as well, no matter how far behind in population I am... it is always a good feeling to see the manufacturing goods rank is better than the population rank, it means you're playing with beginners who just had good luck in the beginning
)you can search for the explanations. In the past half year or so, all demographic topics have had a thread discussing what they mean. 
