Category Archives: Students

Stages à Montréal pour le printemps et l’été 2027 (Mitacs Globalink)

L’été prochain, on propose 3 stages, à Montréal.

Le site de https://www.mitacs.ca/fr-ca/ va ouvrir dans les jours à venir (oui, il faut s’y prendre très en avance). Pour faire simple

  1. on a proposé des sujets
  2. les étudiants postulent sur la plateforme de mitacs à la fin de l’été
  3. cet automne, mitacs fera une opération de couplage étudiant(e)s – stages : on va recevoir pour chaque sujet une liste de 10 étudiant(e)s intéressés, et on commence des entrevues
  4. on propose une liste d’étudiant(e)s qui nous intéresse
  5. mitacs va refaire un couplage, entre les préférences des étudiant(e)s et des responsables des stages
  6. quand on couplage est fait, on est prévenu, mitacs va aider sur la partie logistique et financière, nous on va gérer le volet scientifique.

C’est simple, par contre, il faut que les étudiant(e)s se manifestent et s’inscrivent sur la plateforme avant le 15 ou 16 septembre. Après, ça sera trop tard.

Global Mathematics Lecture IV, Kyoto University

this Fall I will give the “Global Mathematics Lecture IV” at Kyoto University, a series open to all graduate students across the university (not limited to mathematics). My talk will focus on “algorithmic discrimination in predictive models”, based on Insurance, Biases, Discrimination and Fairness (published last year), with a particular emphasis on applications in insurance, a topic especially relevant for students in the actuarial/insurance track of the MSc program in the Department of Mathematics. Looking forward to engaging discussions with the students!

Summer School in Warszawa

In a couple of days, I will be in Warszawa (Warsaw) for a Summer School, to give a short course on Insurance, biases, discrimination and fairness, invited by Łukasz Delong. Slides are now available.

This course will provide a state-of-the-art, on fairness and discrimination, in the context of insurance pricing (and more
generally, predictive models). As explained by Avraham et al. (2014) “insurance companies are in the business of discrimination. Insurers attempt to segregate insureds into separate risk pools based on the differences in their risk profiles, first, so that different premiums can be charged to the different groups based on their differing risks and, second, to incentivize risk reduction by insureds. This is why we let insurers discriminate. There are limits, however, to the types of discrimination that are permissible for insurers. But what exactly are those limits and how are they justified“. First, we will come back to the specificities of predictive models in insurance. We will come back to the different places where a potential discrimination can intervene, by insisting on the possible biases in the data, in the models. We will present in particular the regulations in Europe and North America. In a second step, we will see how to quantify a possible discrimination, insisting on the main measures of “group-fairness”, before discussing the individual approach, in particular in relation with the causal approaches. Indeed, the central question of discrimination is “would the price have been different if this person had been a man instead of a woman“. We will see how to build a counterfactual allowing to quantify a possible discrimination. Finally, we will see how to correct a discrimination, insisting on the in-processing (throught penalized models) and post-processing approaches (using optimal transport). This course will be based on the recent textbook, Charpentier (2024) Insurance, biases, discrimination and fairness. Springer.

Internships, Spring and Summer 2025

The platform Mitacs Globalink Research Internships is now open, for next Spring, and next Summer.

On the page https://www.mitacs.ca/our-programs/globalink-research-internship-students/ there is a “Apply now!“. In the “project” folder, there is a form to fill. Just type “charpentier” under Faculty Last Name

Then you will see three propositions,

Projets will be co-supervised with postdoctoral fellows and students from the research team. Please feel free to apply, if you are eligible.

Bayesian Improved Surname Geocoding to predict “Race” in the U.S.

After Florent last week, this Wednesday, Ana (Patrón Piñerez) will give a talk to conclude her internship in Montréal (supervised with Agathe), on Bayesian Improved Surname Geocoding to predict “Race” in the U.S.

This study focuses on predicting race within the United States, a topic of significant sensitivity due to legal prohibitions against discrimination based on ‘race, color, or previous condition of servitude’ (Civil Rights Act of 1866, 1964). At the same time, due to the rising prevalence of big data systems, insurers are increasingly required to adhere to regulations such as Colorado SB21-169, which mandate demonstrating non-discriminatory practices toward sensitive attributes such as race. In this context, our research explores various methodologies for race prediction. We begin by examining pre-Bayesian approaches that utilize geolocation and surname data, progressing to Bayesian methods that integrate these sources. Specifically, we discuss Bayesian Improved Surname Geocoding (BISG) and its adaptations. Challenges associated with these techniques, such as handling zero counts for minorities and data scarcity, are also addressed. Finally, we propose a novel strategy known as nested dichotomies, rooted in the BISG algorithm. Unlike traditional multiclass prediction, this approach involves sequential binomial predictions structured within a nested framework.

Exploration des Techniques de Transfert d’Apprentissage sur des Données Climatiques

L’été avance. Florent, qui est en stage depuis presque 4 mois, va faire un exposé demain au séminaire d’été des étudiants, sur le thème “Exploration des Techniques de Transfert d’Apprentissage sur des Données Climatiques”

Le transfert d’apprentissage (ou Transfer Learning) représente une avancée notable dans le domaine de l’intelligence artificielle. Cette technique repose sur l’idée que lorsqu’un modèle est bien entraîné et performant dans un contexte donné, on peut utiliser ce savoir-faire dans un autre contexte, différent mais lié, pour améliorer la modélisation, notamment lorsqu’on dispose de peu d’informations sur ce dernier. Cependant, les performances des modèles de transfert d’apprentissage varient, et le choix de transférer la connaissance n’est pas toujours optimal. La principale difficulté réside dans la capacité à garantir les performances du transfert afin de justifier ce choix. Cette approche pourrait s’avérer particulièrement précieuse dans le contexte de l’analyse des données climatiques. En effet, les modèles utilisés dans divers secteurs pourraient bénéficier des techniques avancées de transfert d’apprentissage pour améliorer la précision des prévisions et optimiser les stratégies d’adaptation et d’atténuation du changement climatique. De plus, le transfert d’apprentissage permet de réutiliser des modèles existants, réduisant ainsi les coûts temporels et écologiques liés à l’entraînement de nouveaux modèles. Cette méthode pourrait rendre l’analyse climatique plus efficace et durable, tout en économisant des ressources précieuses.

Pour l’anecdote, il y a presque 5 ans, je donnais un exposé sur Paris “The Challenge of Predictive Models (for Rare Events)” (les slides sont toujours en ligne). Mes centres d’intérêt n’ont pas trop évolués,

Contribution of machine learning in modeling rare values and imbalanced data

This morning (Montréal time), Samuel Stocksieker defended his PhD thesis entitled “contribution of machine learning in modeling rare values and imbalanced data“. Cécile Capponi, Marianne Clausel, Julie Josse, Frédéric Planchet and  Anne Sabourin, Christian-Yann Robert and Stéphane Loisel were in the jury,

the work is structured around major axes: Imbalanced Features and Imbalanced Regression. The first axis addresses the issue of feature imbalance, that is, when it concerns the attributes and not the variable to be explained. The first solution involves adjusting the distribution of a continuous covariate relative to a given target distribution. It proposes to combine weighted resampling and synthetic data generators. This strategy notably allows to deal with selection bias: when the distribution of the covariate in the training sample is significantly different from that of the population. A second solution is proposed in the context of multi-supervised learning, particularly with autoencoders. It relies on a new metric aimed at balancing the influence of variables during learning and is applicable not only to supervised and unsupervised models, but also to generative models such as variational autoencoders. The second part deals with the issue of regression from imbalanced data. Various preprocessing solutions, including synthetic data generation, are proposed. Initially, we propose to explore the initial data space by introducing new generators and methodologies to address the specific case of regression. We then propose to immerse the data in a latent space in order to provide a more conducive framework for synthetic data generation.

Apprentissage par renforcement, jeux et collision

Ce matin, Suzie Grondin nous expliquait les applications du RL (apprentissage par renforcement) en théorie des jeux, pour comprendre la collusion, pour la fin de son stage (6 mois de césure à l’ENSAE Paris) 😪 . Avec un lien avec le papier de Luc Rocher sur les approches adversariales, et une rapide introduction au “Offline-to-Online Reinforcement Learning”…

Merci à toute l’équipe (Philipp Ratz, François HU, Agathe Fernandes Machado, Dante Mata López) qui est venu l’écouter, ainsi que Louis Abraham… Superbe travail ! on veut un papier maintenant 😉 !