Shipping? Common or Rare?

Shipping in Traveller is more likely to resemble 16th century shipping, where
they shipped stuff from one place to another because X didn't exist at point B.
But how much of this will be going on, when the basics oflife can be provided
with a planet or a system?  There will still be markets for stuff like tea, and
furs, exotic stuff from far off places for people who have a lot of money to
blow, but fewer raw materials.

Another factor is can a TL 12 planet produce *all* the goods required by a TL
12 economy?  Can the same planet or system produce consumer goods, power
plants, jump drives, computers, weapons, air rafts, body armor and hulls?  I
tend to think not.  I think that it's much more likely that planets will
specialize on high tech products, and will export only computers, or only air
rafts or grav tanks.  Supposedly every developed planet has a starport andcan
build spaceships, but that doesn't seem likely.  It seems more likely that only
one planet in a dozen will make a business out of building ships, probably
making the hulls, and importing all the rest.  To do *all* of the economic
activity involved in making a business out of building ships would wear out a
planet quite quickly, I would think maybe a couple of decades.

Can we take these factors into account on shipping charts?

Jim Baranski