This author (never heard of him) is playing with statistics. The north had 2-1/2 times the population of the south and 3 times the wealth.Most of those outbound ships arrived empty, because there wasn't sufficient demand for imports to justify sending them directly to the south..
Think about it -- those figures actually work against the point that you're making. The reason that tariffs were low was because they were working as intended -- southerners were being forced to choose between very expensive northern goods and even more expensive (because of the tariff) imported goods. The south chose to pay the north in higher prices instead of even higher tariffs. What effect does the current steel tariff have on the U.S.? You got it -- it drives out imported goods and forces business to buy American steel. In the case of the south before the Civil War, southern dollars were being diverted to the north instead of to other countries.Again, this author is making you believe that his statistics prove a point when they actually work against him. I don't know whether he's intentionally lying or if he just doesn't understand economics.
All things being equal (other than price), faced with a decision between something priced for $1 (northern) and .85 (european) the choice is obvious. With tariff applied it becomes a choice between $1 and $1.11 (30% tariff). Raising it to 47% made it $1.25. But did the North leave their price @ $1? Or did it get raised to $1.15? Either way, northern pockets were filled with southern monies.
Despite this, some would have us believe that southerners were not affected by tariffs, or that southerners were not paying the duties (due to where the goods were shipped), yet no one can provide documentation of northerners protesting higher tariffs. They obviously think that southerners protested higher tariffs on behalf of northerners. < /sarcasm >