Development of yields per hectare of wheat, rye, and barley in five-year averages from 1848-1852 to 1908-1912
Statistics compiled from E. Bitterman, Die landwirtschaftliche Produktion in Deutschland 1800-1950 [Agricultural Production in Germany 1800-1950], Kühn-Archive (Faculty of Agriculture, Martin Luther University, Halle-Wittenberg) 70 (1956).
Printed in Hermann Aubin und Wolfgang Zorn, ed., Handbuch der deutschen Wirtschafts- und Sozialgeschichte [Handbook of German Economic and Social History]. Stuttgart, 1971-76, vol. 2, p. 518.