hum? i fear you are mistaken:
what you changed is the percentage of goods from the stock that should be traded to your people instead of used for stockpile reserves.
i play normally the GC with US and set everything to 80%.
if you have NO goods in stock, like MFGs, they will not be sold. to lower MFGs percentage makes only sense whenever you have few and want to gather them for any building activity.
same is true for coal!
IMPORTANT is how many goods you truly have.
the goods are parted into groups and can substitute each other in this groups.
if i satisfy all needs with the US and set tariff to upper limit (to sell more own goods instead of foreign ones, so decreasing foreign market penetration), i do gain an average of 0,56% happiness each turn.
in end 1850s i have a that stable economy that i do not need taxes. only 15% tariffs.
then i get an increase of 1% average national happiness each 4-5 turns.
be aware, you can sell as much as you want, if MILITANTISM is higher than about 5% you will get very angry people.
the total impact depends then from your political situation in F1-ledger. barely predictable.
if i fulfill all need during the 1850s and set excise tax, corporate tax and tariff to the upper maximum, i can hold a steady state while the gain from sold goods covers the losses from taxes.
but then i can get only increases from reforms and they must outweigh losses from economic crisis events and other events.
taxes and tariffs have different impact on different groups of population
see:
http://forum.paradoxplaza.com/forum/showthread.php?561492-How-Taxation-works-in-PON&
but please, just take it as a examle of the impact. his file shows the right effects, but the calculations he did are highly misleading and even wrong, for he assumes that taxes hit all provinces with every degree for the population classes at the same time.
however, they hit only the population IN a province, thus provinces and areas are effected in different ways, depending what social classes are given. thats why you get the GENERIC messages showing that some areas are unhappy, while others are not experiencing major unhappiness...