Statistical information about Singapore is often patchy and incomplete, though not necessarily unavailable. We know for example how fast the population is growing, but to try and figure out how much of this growth is natural, i.e. born here, as compared to immigrants requires a bit of detective work.
Here are some interesting ideas. Bear in mind I am neither a statistician or demographer....rather a kaypoh as usual... :
in 2000, when the last census was done, we had a population of 3.210822 million, out of which, 2.647393 were born in Singapore. So that can serve as a convenient starting point for us. Since population growth every year is birth rate - death rate + immigration rate, we can calculate natural population growth by just using birth rate - death rates. These rates (annually since 2000) have been conveniently provided for us here (birth rate), and here (death rate).
Plugging these into my outdated Excel spreadsheet allows me to chart the natural growth of our population since 2000. (Probably only an approximation since the birth/death rates are for whole population rather than just for Singapore born folks. But it gives us an idea.)
Accordingly, if we had gown naturally we should have had a population of 2.707 million in 2009.
By contrast, our 2009 population is 4.988 million, out of which 3.734 million are 'residents' (citizens and PRs), i.e. approximately 1 million residents in Singapore were not born locally. Interestingly, as our current citizens are 3.201 million, it implies that about 0.5 million citizens were not born in Singapore since 2000. Also our total population is almost twice as numerous (4.988/2.707) as those Singaporeans who were born locally.
Interesting. I can't wait for the 2010 census data.