Improving Empire Designs

[Cipher7071]

I've been tinkering with empire designs for several games now, and I want to learn how to make some specific improvements. Up to this point the results of these adjustments have been largely trial and error.

During empire set-up there are a number of racial modifiers and cultural modifiers that are given as percentages to be either added or subtracted. My problem is that I'm having a devil of a time locating the base values that these are intended to modify.

For instance, I can add 10% to the value for a spaceyard 1, but I can't seem to find what the base rate is for a homeworld. If I have a specific value in mind that I want for a planet (or homeworld), I want to be able to figure out what percentage I need to change any particular attribute to produce that desired value.

So, the question is: Where do I find the base values that these modifiers are modifying?