Been a few years since I last posted, but well, FreeTrav, you asked for
this.

How does having multiple economically-interesting worlds in a system
affect system trade stats?

As I'm a GT guy by preference (with a couple of TNE books kicking around
in storage), I'll frame this in GT terms.  I'm saying
economically-interesting worlds have a WTN of at most a half point below
the biggest in-system WTN.

Frinstance, IMTU, the Iderati system has undergone somewhat more
development than in canon, sporting two hi-pop hi-tech worlds
Iderati III: Pop 20 billion, GTL13, Subsector capital, Industrialised,
Class V port - UWTN is 6.5, unmodified by port to give WTN 6.5.  Per
capita GWP is Cr34,160/a, GWP is TCr680/a
Iderati V: Pop 2 billion, GTL12, Rich, Agricultural, Class V port (bent
somewhat from GT:FT guidelines for sake of argument) - UWTN 6.0,
unmodified by port to give WTN 6.0.  Per capita GWP is Cr28,800/a, GWP
is TCr57/a

In this situation it doesn't affect WTN, but would easy access to a
GTL13 world drag Iderati V up to GTL13? (Yes, I was going for
"technoeconomic juggernaut" feel).

Trade codes would obviously be:
iderati III: Cp In
Iderati V: Ri Ag

If Iderati Vs population was under a billion, or its GTL was 11 or
lower, its WTN would drop to 5.5 and thus below my
"economically-interesting" cutoff.  Since it doesn't, is such a system's
trade codes the union of its interesting worlds' codes?

Ie, for external purposes (and to save me having to take a crowbar to
PyRoute's guts):
Iderati system:
WTN 6.5
Trade codes Cp, In, Ri, Ag

Similarly, would three economically-interesting worlds , each having the
biggest WTN in-system, end up boosting overall system WTN by a half
point, in addition to system trade codes being union of all three worlds?