To be precise
The following is from a post I made that is in the middle of a very active thread on the scenario forum:
I have researched how the colonists.csv file works. See below for details. Also, see
here for details on the issue and the research.
The following information is useful for evaluating whether colonization (i.e. the number of colonists) is as desired in the IGC, and for making future changes. Many changes have been made to colonists.csv to tweak colonization. I believe many of these changes are incorrect, now that the mechanism for colonists.csv is known.
How many colonists do you get a year?
1) 0 colonists unless you have a port, no matter what.
2) 1 colonist if you have a shipyard.
3) Religion. I tested all religions but Pagan.
* Catholic, Shia, and Shiite get no extra colonists
* CRC and Protestant (Lutherin) get 1 extra colonist
* Reformed gets 2 extra colonists
4) Getting a Conquistedor or Explorer gives 1 colonist when you get them.
5) And the big one. The combined values of colonists.csv and traders.csv are used. Basically, add the values together and divide by 100 (no remainder) and you get that number of additional colonists. There is absolutely no % chance involved. You get a fixed number of colonists based on this calculation - it never varies. The calculation is wierd, because some combinations that add up to exactly 100 (or 200, etc.) will not result in the expected number of colonists (it will be 1 less). I have tried all kinds of schemes to figure this quirk out, and none work. Multiples of 25 work.
Factors not involved in "how many" colonists there are:
1) Colonial dynamism tag. This is a calculated value by the game and always equals the result of the calculation in #5, above. It does not matter what this is set to, it will be changed by the game.
2) Stability.
3) "colonialnation" and "colonialattempts" tags in the scenario and save files. I was not able to determine what these do, though I recall posts from months ago indicating that first time colonization attempts are harder - I did not see this.
How to use colonists.csv and traders.csv
One thing is certain, tweaking the number of colonists requires both files to be taken into account, and no value that is not a multiple of 25 is very useful. And, it does not matter which file has any, or the larger values - all combinations work the same. Any combinations that do not add up to a multiple of 100 are useless (i.e. the excess will be thrown away).
A country need not be in both files. In fact it is a complication. There are questions about whether there are limits to how many countries can be in one of these files. If there is a limit, then I suggest keeping colonists.csv as is (i.e. what countries), and use traders.csv for new countries. Credit to Errant One for this suggestion! Note, a country does not need to be in this file, it will get colonists based on other factors like shipyards.
Why are there two files?
Who knows? I've tested and cannot find any use for the two files by the game. These files do not affect how likely the ai is to create a colony or create a TP. This is done via the ai files. The best theory is that these files were originally intended to support the colony vs. TP decision, and further, that the values in the file were percentages. However, the way the game works now, these files are used solely to calculate how many colonists are given per year.
