That measure inherently excludes the “wealth” represented by ownership of enslaved people. It includes what those people produce, but the “per capita” measure also includes enslaved people in the denominator.
The production of enslaved people represented a small fraction of the economy—about 5% of GDP during the peak of the cotton boom: https://fee.org/articles/no-slavery-did-not-make-america-ric... see also https://jacobinmag.com/2019/08/how-slavery-shaped-american-c...
More importantly, you can’t increase a country’s overall level of production by enslaving people. Its basic economics—unfree labor misallocates labor resources to industries controlled by slave owners. Slavery obviously redistributes wealth from enslaved people to a slaveholding aristocracy, but that comes at the expense of economic growth for the country overall. This is true both theoretically and empirically. As shown in the GDP chart linked above, the end of slavery didn’t produce an economic collapse, as you would expect of it really was responsible for America’s productivity. There was not even a dip. In fact, ending slavery made America richer, exactly as economic theory would predict: https://www.econlib.org/archives/2014/09/ending_slavery.html
It was not just reallocation of wealth like tax, it completely changed his money were made.
I don't really understand this argument. Surely reducing one of the operating costs of doing business to zero leads to economic growth right? In your hypothetical scenario, wouldn't the business owner just invest some of that profit into growing the business, thereby increasing productivity?
Alternatively, they can lower their prices in order to beat competitors. If they're producing a commodity, this can have the knock-on effect of lowering the price of finished goods using that commodity.
Another point of comparison is, in places where they discover "free resources" like petrochemicals, like Norway, that does lead to prosperity, doesn't it?
Sure, but imagine the alternative where the slaves are paid workers instead: then the same money that you use to invest into your business in slave scenario is instead spent by your workers on other businesses, which then use it to produce other things or invest in their businesses. Again, slavery, instead of increasing total wealth, just redistributes it in favor of slaveholders.
You are however averaging production to slaves too. So in countries where blacks outnumber whites you get much smaller wealth then what contemporaries commented on.
The alternative scenario is north in any case. The kind of society and production south was is plain impossible without slavery. It just did not exist.
Is it really though? For instance, in the post-war period of the 1950's which is often taken as the period where the American Dream was in full force, organized labor was much stronger in the US than it is today, and a huge chunk of the population was essentially inserted into the middle class through the GI bill, which was really a social welfare program when it comes down to it.
I think the degree to which individual grit gave rise to American prosperity is often over-stated, and the degree to which it was a result of collective action is often overlooked.