Measuring Away the Importance of Institutions: The Case of Seigneurial Tenure and Agricultural Output in Canada East, 1851 Vincent Geloso 1 Abstract: This paper argues that the 1851 census of Canada East (modern-day province of Quebec) requires a set of important corrections. Using corrections based on ethnic origin composition, I demonstrate how largely wheat and oats yields were underestimated in Canada East. More importantly, I argue that the measurement errors are not randomly distributed and that they bias against attempts to test the role of institutions. I show how new methods of correcting the data change our interpretation of the state of Lower Canada and Upper Canada in the mid-19th century. While this correction may seem minor, it shows that in the past, the data took a form that was biased against numerous hypothesis concerning land tenure institutions. Highlights 1. The flaws in reporting volume and area units in the agricultural census of 1851 of Canada East follow ethnic lines (French versus English) 2. Since the French tended to mix with the English, but not the reverse, the measurement errors are found predominantly in mixed areas. 3. Correcting for volumes and areas along ethnic lines shows that output and productivity in mixed areas is underestimated. 4. Previous corrections for the metrological pitfalls of the 1851 census underestimated grain yields. 1 Vincent Geloso is a PhD candidate in economic history at the London School of Economics and Political Science and a course lecturer in economics at HEC Montreal, he can be reached at v.geloso@lse.ac.uk ; Acknowledgments to Manuela Volaco, Jari Eloranta, Michael Hinton, Kris Inwood and Vadim Kufenko