Biological innovation and productivity growth in the antebellum cotton economy

"The Cliometrics literature on slave efficiency has generally focused on static questions. We take a decidedly more dynamic approach. Drawing on the records of 142 plantations with 509 crops years, we show that the average daily cotton picking rate increased about four-fold between 1801 and 1862. We argue that the development and diffusion of new cotton varieties were the primary sources of the increased efficiency. These finding have broad implications for understanding the South's preeminence in the world cotton market, the pace of westward expansion, and the importance of indigenous technological innovation"--National Bureau of Economic Research web site.