With HTTT local and global cot_gravity was added as province and country modifiers respectively. Does anyone know what they do? They are not used in the base game (there is an entry that has been commented out in the governments.txt though).
I was thinking they might be a modifier to the location chosen when a random CoT is spawned but that's very hard to test...
Neighbor provinces are more likely to trade their goods in cot with higher gravity. AFAIK.
The value applies to existing COT's, and is applied in integers. The number of the modifier is added to the number of provinces naturally trading through this COT, to widen its catchment area.
20 provinces trade through Lübeck.
local_cot_gravity = 4
Now, 24 provinces will.
Obviously, if you applied these modifiers to all COT's the world over, they'd cancel out each other.