Turning Water into Wine New Methods of Calculating Farm Output and New Insights into Rising Crop Yields during the Agricultural Revolution Liam Brunt Nuffield College, Oxford and Ecole des Hautes Etudes en Science Sociales, Paris Liam.Brunt@nuf.ox.ac.uk Abstract Constructing an agricultural output series requires a rational economic basis on which to convert one crop into another, and a conversion method using only the information which we have at our disposal. The traditional method fails on both counts. We develop two alternative methods. The first is extremely parsimonious but imprecise; the second is less parsimonious but allows us to isolate the effect of different crop rotations on wheat yields. We compare the three methods using the farm dataset compiled by Arthur Young on his tours of England and Wales during the Agricultural Revolution and we show that new fallow crops substantially increased the wheat yield.