[douglas]

Examples all assume stock game:

Good homeworlds, low tech start, neutral culture, 110% construction aptitude:

A good homeworld is always Large size (hardcoded), and homeworlds always start at normal maximum population for their size, so the homeworld has 4000 population (PlanetSize.txt). The Advanced Storage trait increases the actual maximum to 4800, but does not affect starting population.

The first population modifier in Settings.txt with a max pop greater than 4000 is the 51st entry, with a space yard modifier of 150. The "SY" designation here is actually misleading, as this particular modifier applies regardless of the presence of a space yard. In fact, it is the only modifier that does so. If you scrap your homeworld's space yard, it will have a build rate of 2000 (base for planets from settings.txt) * 150% (population) = 3000 in all resources independent of other factors.

If you keep the starting space yard, however, then your Construction Aptitude characteristic applies, adding another 10%. Note that this is added to the population modifier before multiplication, so your homeworld's build rate would be 2000 (from Space Yard Facility I) * (150 + 10)% = 3200.


Now for a more extreme example:
Good homeworld, high tech start, Engineers culture, 150% construction aptitude, Hardy Industrialists advanced trait, Temporal Race advanced trait

As before, the large homeworld has 4000 population which provides a base modifier of 150%. The Engineers culture adds 5% to space yard rates (Cultures.txt). Your extreme Construction Aptitude adds another 50%. Hardy Industrialists adds yet another 25%, but for planetary space yards only (RacialTraits.txt). The total modifier is 150 + 5 + 50 + 25 = 230%.

Your homeworld's build rate would be 4500 (Temporal Space Yard Facility III - high tech start plus racial tech, Facility.txt) * 230% = 10350.

Now suppose you build a space yard base first thing with this setup. Bases don't have population modifiers, so nothing in settings.txt applies. Hardy Industrialists only works for planets, so you don't get its 25% here. The Engineers bonus and Construction Aptitude both still apply, however, for a modifier of 100 (base) + 5 + 50 = 155%. Since there is no temporal version of the space yard component, you're stuck with an ordinary Space Yard III. Build rate 2000 (SY III, Components.txt) * 155% = 3100.