A new working paper confirms the theory slavery did not build the American economy.
Ager, Phillip, et al. “The Intergenerational Effects of a Large Wealth Shock: White Southerners After the Civil War.” The National Bureau of Economic Research, Mar. 2019, http://www.nber.org/papers/w25700?sy=700.
The Abstract for this paper reads:
“The nullification of slave-based wealth after the US Civil War (1861-65) was one of the largest episodes of wealth compression in history. We document that white southern households with more slave assets lost substantially more wealth by 1870 relative to households with otherwise similar pre-War wealth levels. Yet, the sons of these slaveholders recovered in income and wealth proxies by 1880, in part by shifting into white collar positions and marrying into higher status families. Their pattern of recovery is most consistent with the importance of social networks in facilitating employment opportunities and access to credit.”
Essentially, slaves in the South were beneficial for farmers in terms of profit and the end of the Civil War, emancipating slaves from their masters, led to a causal loss in resources/money. However, this was quickly made up for and recovered by the sons of these workers.
This indicates whatever was gained from slavery could not have been large enough to create any sort of long term economic loss for America. Plenty of other research has been done that would imply this result; this study is important as it provides a full impact analysis.