A study in Rashomon curves and volumes: A new perspective on generalization and model simplicity in machine learning

The Rashomon effect occurs when many different explanations exist for the same phenomenon. In machine learning, Leo Breiman used this term to characterize problems where many accurate-but-different models exist to describe the same data. In this work, we study how the Rashomon effect can be useful for understanding the relationship between training and test performance, and the possibility that simple-yet-accurate models exist for many problems. We consider the Rashomon set - the set of almost-equally-accurate models for a given problem - and study its properties and the types of models it could contain. We present the Rashomon ratio as a new measure related to simplicity of model classes, which is the ratio of the volume of the set of accurate models to the volume of the hypothesis space; the Rashomon ratio is different from standard complexity measures from statistical learning theory. For a hierarchy of hypothesis spaces, the Rashomon ratio can help modelers to navigate the trade-off between simplicity and accuracy. In particular, we find empirically that a plot of empirical risk vs. Rashomon ratio forms a characteristic $\Gamma$-shaped Rashomon curve, whose elbow seems to be a reliable model selection criterion. When the Rashomon set is large, models that are accurate - but that also have various other useful properties - can often be obtained. These models might obey various constraints such as interpretability, fairness, or monotonicity.Comment: Revisited sections 3, 4, 5, 6, 7, and

In Whose Interest? The Early Years of the First Caisse Populaire, 1900‑1945

In 1900 Alphonse Desjardins opened the first caisse populaire at Lévis, a small town located across the St. Lawrence from Quebec City. Many historians have seen the establishment and the early operations of the Caisse populaire de Lévis in heroic terms, as it proved to be the beginning of the development of a vast cooperative movement. Desjardins and his colleagues were described as disinterested men only desirous of providing financial services to the poor. This characterization has a certain validity, as credit was made available that could not have been found elsewhere. Nevertheless, such a perspective ignores the fact that the founders of the caisse and their successors were members of the local petite bourgoisie who were profoundly insecure regarding their place in an industrializing Quebec. As a result, the operations of this caisse up to the end of World War II were not always in the best interests of the poorer elements of Lévis.En 1900, Alphonse Desjardins ouvrait la première caisse populaire à Lévis, petite ville sur le Saint-Laurent, en face de Québec. Beaucoup d'historiens ont parlé en termes élogieux de la fondation et de l'établissement de la Caisse populaire de Lévis, car ils ont vu dans cette initiative l'origine du vaste mouvement coopératif. Ils ont décrit Desjardins et ses collaborateurs comme des hommes désintéressés, uniquement préoccupés de fournir des services financiers aux pauvres. Une telle présentation ne manque pas de fondement, étant donné que la caisse populaire offrait aux pauvres le crédit qu'ils ne pouvaient obtenir dans les autres institutions financières. Néanmoins, cette interprétation ne tient pas compte du fait que les fondateurs de la Caisse populaire de Lévis et leurs successeurs appartenaient à la petite bourgeoisie locale, et que celle-ci souffrait alors d'une profonde insécurité dans un Québec en voie d'industrialisation. En conséquence, pour la période allant de sa fondation à la fin de la Deuxième Guerre mondiale, la Caisse populaire de Lévis n'a pas toujours servi les meilleurs intérêts des éléments les plus pauvres de la population

Making Kouchibouguac: Acadians, the Creation of a National Park, and the Politics of Documentary Film during the 1970s

The documentary film Kouchibouguac, released by the Office national du film (ONF) in 1979, allowed Acadians – who had been removed from their lands to allow the creation of the national park of the same name – to tell their stories. This article explores the making of the film, with a particular focus upon the difficulties experienced by Acadians trying to find their voice within the Québécois-dominated ONF. It also reflects on the form of the film as well as the impact that it had within an Acadian population that was divided over the sporadically violent opposition to the park. Sorti en 1979, le film documentaire Kouchibouguac, de l’Office national du film (ONF), a permis aux Acadiens qui avaient été forcés de quitter leurs terres afin de permettre la création du parc national du même nom de raconter leur histoire. Cet article explore la production de ce film en portant une attention particulière aux difficultés que les Acadiens ont rencontrées en essayant de trouver leur voix à l’intérieur de l’ONF, dominé par des Québécois. Il examine aussi le film sur le plan de la forme ainsi que l’impact qu’il a eu parmi une population acadienne divisée par l’opposition parfois violente à la création du parc