[c_of_red]

You are seeing that 2.5% as only applying to ships. Think of it as a production efficency that can be transferred to any part of the system. You can transfer it to research, non-ship production, what ever you feel will give you the greatest advantage. I'm not far enough into this particular game to check that yet, but if you cannot switch resources between needs, then this will be the first 4X game I have ever seen that didn't allow that. It is such a fundamental point that the whole game would be bogus if it wasn't allowed. It seems as if the number a ships that can be built is limited within a time slice by the number of shipyards. So if that 2.5 percent was used to build more shipyards then you would end up being able to build more ships over a given period of time. Compounding interest was an anology and an example NOT an event. I used it in an attempt to illustrate how a small advantage can be leveraged into a huge advantage over time.
The whole thing is a SYSTEM; imput->processing->output.
I also think my 25% was a LOT closer to correct then 2.5%. the Saving in Hull metal alone would be on the order of 3.141 times the radius squared, over a given length. Note, I have switched back to the real world. So on bigger ships the savings would be several hundreds of times. So for any given ship size you could produce several dozen (prehaps humdreda) open ships to each hulled ship using the same amount of metal. The cost savings wouldn't be as much for all the other bits, but they wouldn't cost more either, or at least not much more for those parts that required atmosphere.