Did slavery make economic sense?

Read the following article and summarize what the author is trying to tell the reader about slavery's impact on the economy: Plus add your analysis of the article..did you agree with the author's theory or view? Please only summarize ONE article
Did slavery make economic sense? by C.W. and A.J.K.D. http://www.economist.com/blogs/freeexchange/2013/09/economic-history-2