Ok, I found this:
I have done this for maps, but they are not showing up in the game.
Very good questions and really not that clear when you're playing the game.
1) yes.
2) Basically, you need to have a trade road connection to their lands, open borders and you need to see their cultural borders. But it's a little more complicated then that. So I'll let DanF5771 do the explaining as he did in excellent job in this post of his.
If you can't trade with a civilisation after thesymbol appeared, then they are benefiting from trade routes with you, but you aren't benefiting from trade routes with them.
, and the slider is at 60% 
, then 4 are being converted into 
for the treasury? So improvements such as the bank are only modifying the 4 ?
Yes. Therefore, Bank + Market + Grocer together give you +100% cash.
left over from the slider would be converted into 8 for my treasury.I had that ah-ha! moment while playing Civ regarding building modifiers: they only modify after commerce has been fed through the slider. So is the following understanding correct?
If a city produces 10
But how do the modifiers stack? Are they simply added to together?
commerce and merchant specialist and shrines which produce gold gold. Gold is just one of the parts into which commerce is divided, but sources which produce gold directly of course aren't divided anymore (by the slider).
Indeed. Depending on the size of the map and how many corporations you found and spread, it's perfectly feasible to get well over 1000 gold per turn in income from the headquarters. All you need is a Market/Grocer/Bank and Wall Street, and a whole lot of executives. It's certainly a benefit worth putting in the effort for - not to mention the individual advantages of the corporations themselves.That's true.
It's the difference between tile improvements and trade which produce commerce
Wall Street indeed is often best placed in a city which produces a lot of gold and not a city which produced a lot of commerce. Sometimes this can be the same, but it is not necessarily so. A (great) shrine city or a city with lots of merchants or a city with a corporation headquarters is often the best place for Wall Street. Such a city produces lots of gold independent of the slider.
No. However, the new city may have extra shared tiles with the other civ, which might give negative diplomatic points due to interfering borders. By the same token though, the city flip might reduce the number of shared tiles with the other civ, which might remove negative diplomatic points and give a net positive outcome. It just depends on the situation.
