Re: [GZG] Re: Gzg-l Digest, Vol 13, Issue 9

[Paul J Foster <pj_foster@xxxxxxxxxx>]

gzg-l-bounces@xxxxxxxxxxxxxxxxxxxxxxx wrote on 08/05/2006
20:33:01:

> Beth muttered:
> >Laserlight's plausible story telling approach is fine
> 
> Let's say you start with 10,000 colonists, and add immigrants at the
> lesser of 60,000 immigrants or 10% of the base population per year.
> After 100 years, with a 3% growth rate you get about 16 million; 
> with a 2% rate you get 9.5 million.

Many estimates of growth rates seem unreasonable to
me.  If we take Earth as an example, UN figures show that world population
growth peaked in about 1970 at 2% per year.  Prior to 1950, it never
rose about 1% and since 1970, population growth rate has been at a steady
decline.  In 2000, annual growth was 1.39%.  UN forecasts: 2010
1.15%; 2020 0.98%; 2025 0.86%.

Of course, growth rates vary considerably by country
- but typically, the better educated, richer, more technically advanced
countries have lower growth rates.  In fact, if it were not for immigration,
many western countries would see populations declining.

Therefore, I suspect that the above example growth
rate is highly unlikely.  Let's take some extreme figures - lets say
the population doubles every generation. (i.e. every person finds a partner
and they have 4 children who all survive)  Lets have a new generation
every 20 years.  Starting with the 10000 colonists, mentioned above,
that would mean that after 20 years - you'd have 20000, after 40 years
40000, after 60 years 80000 after 80 years 160000 and after 100 years 320000.
 Now that's an astronomical rate of increase for a population - but
it's nowhere near 16 million.  Of course - there may have been massive
immigration and for any kind of 'population growth' model, it's the immigration
that will be the key growth driver - rather than natural growth.
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