Where did DiLorenzo get his figures on the % of the US tariff paid by the South?

I recently came across an apparent refutation of Tom DiLorenzo’s assertion that the South paid 75% of the US tariff before the war. It was a post quoting a passage in James McPherson’s book North and South, re-quoted in full here:

It seems as if this refutes DiLorenzo. Has it been rebutted by DiLorenzo himself or others? If so, where?

I was also wondering the same thing. When I read Reassessing the Presidency, I was surprised when I read that the South paid 75%. I’m pretty sure the 90% figure is closer to what it really was.

I thin it is this. We should put this in print somehow

Here’s some information on the U.S. antebellum tariff policy; there are some interesting bits of information that may be relevant to the original question:

http://www.etymonline.com/cw/economics.htm