So, we've all seen planets that are Ri, Ag, In or what have you which would seem to suggest a lot trade might flow in or out of those spots. We've seen planets with little to offer and not much in the way of population. 

Yet, you can have an A class port on some nearly depopulated bit of dirt and you can have a D type in places you'd expect a better one due to population and trade codes. 

So, do various rules iterations' write ups on Starports always treat a Class A Port as a huge port with lots of traffic and a Type D Port as always low volume without any reference to the world, trade code, population, etc?

I ask because then there should be a stronger input to Starport type than the existing population modifiers (if I recall that) suggest and trade codes such punch the odds up of better ports and others would go the other way. 

To me, an A Class Support has to do with how modern it is, what services it offers, and how capable those are... but all of that could (on for instance a small pop Rich planet with good air, water, etc - the kind of place the Rich might go for some outdoorsy stuff). They might well have a modest sized but very well tricked out port. 

Contrariwise, I would think that a planet with an 8-10 pop and Ag, In or similar resource harvesting type of trade code could have a C or D class port (but that it should likely be a B or C based on trade volume one might expect) and if it was a D, it could be a huge, sprawling, frenetic sort of place despite the limitations of services available. 

What do you think? What factors impact Starport size in various iterations? What isn't accounted that ought to be (UPP values or Trade Codes)?

Tom B