I guess I'm being more realistic than I should be...but......
Where would the extra influence come from? Let's say you got two starbases side by side, each one with a party palace. You go to one starbase, party it up, and leave happy. You go the the other starbase, party it up again, and NOW you're TWICE as happy??
From a military point of view having more than one starbase makes sense for obvious reasons.
Here...let me explain my theory (idea) this way......
You have one starbase in a sector. There is one inhabited planet in that sector. That planet has a pop. of 100m. That population goes to that starbase to live it up. So now you have that one starbase making 100m people happy.
Now you have two starbases in that same sector with the same planet etc etc. The population from the planet can't go to both starbases at the same time, ie: I can't be in Florida and California at the same time. So now the population, in effect, divides itself on which starbase it goes to. Both starbases (same civ) possess the same technology. Just for the sake of argument say that now the pop splits itself 50/50 on where it goes. Both groups will leave feeling exactly the same.
I'm not going to be happier if there are two Disney Worlds that are exactly the same. I can only experience one at a time. And why would I go to the other one if it's an exact duplicate of the one I'm already going to?
Here's some numbers:
100 pop
influence of 2 (or whatever # you like)
ONE STARBASE (starbase A)
100 x 2 = 200
TWO STARBASES (starbases A and

A) 50 x 2 = 100

50 x 2 = 100
add the two starbases "influence" together and viol'a! You get 200 still.
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