Shipping lines are very inconsistent when it comes to ship construction. In some games, they launch a ship almost immediately after I plant colonists on Mars. In others, many years pass before they do much. The construction of subsequent ships is also sporadic, with periods ranging from months to years. This is all with well-subsidized shipping lines (so they can afford new ships), and I've never noticed (key word: noticed) a pattern to their behavior (i.e. high vs low cost ships, number of spaceports or shipyards, &c).
So, in the interest of discovering how to generate fast and consistent growth in the civilian sector, here are my questions:
1. What are the precise requirements for a shipping line to build (more) ships? AFAIK all that's needed is two non-zero populations and a shipping line with enough money to buy a new ship, but maybe they won't build a second ship until there's some incentive (i.e. sufficient supply/demand of trade goods or installations, or a third non-zero population)?
2. What does a shipping line look for in a ship design? Again, AFAIK they just need a commercial ship with cargo or passenger capacity. Is there more to it than that?
3. Assuming all requirements are met, what determines how quickly they build new ships? Is there some sort of build rate limitation? Are they limited to one ship per X months or a random chance per annum, and is that per shipping line or for the entirety of the civilian sector?
4. Does CMC construction/expansion prevent ship construction? I do consistently get CMC generation/growth in all games (as annual income approaches 1m).