On Tue, Aug 26, 2014 at 08:47:39AM -0700, Phil Pugliese (via tml list) wrote:
> If trade was really at a MegaVolume level wouldn't just about all
> worlds have been completely saturated w/ TL10+ by now?

MegaVolume is a relative term.  Remember that when we're talking about
tens of thousands to millions of dtons per week, this is not for a
city, state, or even a country.  It's the sum total of all trade for
at least a *whole planet*.  By any human scale, planets are huge.

Maybe if I put it another way: suppose an Earthlike planet is
moderately sparsely populated, with an average population density of
one person per square kilometre of land - say 50% of the total
surface.  By comparison, modern Earth's average land population
density is about 50 people per km^2.  This puts the world somewhat on
the lower end of a pop-8 world.

Let's say 20% of the population live in cities of a million people or
more, 30% in large towns of 100k-1M people, 20% in smaller towns of
10k-100k, and the remaining 30% in villages or isolated settlements.

There are probably about 5-10 cities on the planet.  A "typical"
inhabitant of the planet will live in or near the lower-size end of a
large town, or the upper end of a smaller town, with maybe 90k people.
The nearest city would probably be 2000-5000 km away, a decent length
of trip even with grav technology.  The nearest larger town would
probably be "only" 500-1000 km away, though even at high tech not a
trivial distance.

A planet with very little trade might import and export only 2-4% of
their GDP.  That is, 96-98% of what they want is satisfied by local
services or production.  They're almost completely self-sufficient,
but maybe a few things are cheaper, better, or easier to import
(either regularly or irregularly).  Maybe in return there are some
things that they can supply just a bit better or cheaper than their
neighbouring worlds.

So this average 90k town imports or exports maybe on the order of
10-20 dtons per week.  If every town had its own starport, it might
get a small tramp once per month.  This certainly has the flavour of
something of a backwater.

However, it's very unlikely that every town has its own downport.  The
trade for the world is likely aggregated into one or more highports,
with an orbital and on-world distribution network of some sort.  When
you add up all the backwaters over the whole planet, you get a traffic
of about 50,000 dtons per week despite this planet (and all the others
nearby) meeting 96-98% of their own demand.

So although this insular planet consists mostly of a few moderate
cities and a great many backwater towns that never see a starship, the
planet as a whole still does enormously more trade than a few tramps
can supply.

That's because planets are really big.

- Tim