An early mathematical presentation of consumer's surplus

This paper shows the first presentation of consumer's surplus as a definite integral is in Launhardt''s 1885 masterpiece, Mathematische Begrundung Der Volkswirtschaftslehre. In chapter 32, Launhardt applied integral calculus to derive the consumer''s surplus of a decrease in the freight rate for each consumer at a market point and for all consumers in the whole market area. Launhardt''s analysis is typically reproduced in the modern literature on non-spatial and spatial economics without any acknowledgement of Launhardt. Launhardt''s name deserves to be mentioned alongside with Dupuit and Marhall as an early anticipator of many key elements in the theory of consumer''s surplus.