Trade advantage is confusing. This part of the wiki feels like it's written wrong but I can't play the game right now to see if there's a popup window to tell me the actual modifiers.
It reads to me more like the bigger your advantage (which is based on a complex set of modifiers, per good), the more profit your merchants take from world market trade with your country...
... which confuses me as surely that is bad for industry as the (uncompetitive) cannot afford to employ merchants to purchase or sell, except off goods with a gulf in price difference
... and there may or may not be free money generated or burned from relative pricing?
... does this mean more competitive merchants integrate your economy better into the world market, for better or worse, and weaker merchants make you more autarkic, or at least unable to be advantaged or disadvantaged by world prices?

I still don't know what the purpose of production method and trading centre placement makes.

When I look at trade laws I get confused again.
>mercantilism = export economy
>protectionism = dependent on tariff/subvention choices
>free trade = undercutting and overcharging everyone else
>isolationism = closed borders
Shouldn't mercantilism be ripping off other people, merchants win,
protectionism be either as is (flexible; your choice) or export economy,
free trade be... I dunno, freedom from tariffs/subventions, maybe an arbitrary +5-10% market access increase, maybe an arbitrary increase in trade capacity, maybe reducing the impact of trade advantage to increase goods traded,
and isolationism... yeah that one's fine.
Am I wrong on what these laws mean?

... I still don't know why the industrialists have an opinion on trade. They don't naturally own/work in trade ports (petite boogers) and none of your trade policies expressly benefit mines and factories, even before the world trade update.
It just feels like paradox makes them favour Free Trade because... uhhh paradox said so.