At the intersection between urban sociology and social group sociology, the thesis addresses the phenomena of gentrification affecting historical working-class areas over the last thirty years and their key players, the gentrifiers. Typical of the emerging "new middle classes" in the late 1970s, categorized by the media as "bobos" in the early 2000s, gentrifiers contribute to urban change through their choices and multidimensional investments in the residential space. The first part of the thesis is devoted to the study of generations of gentrifiers in the Pentes de la Croix-Rousse area in Lyon and in the Bas Montreuil area near Paris; it presents their sociological profiles and residential choices from the 1970s to the 2000s. The second part is devoted to the local analysis of the "gentrification work" in which new residents of the Bas Montreuil are engaged, in connection with their social, professional, militant and family trajectories. Based on extensive interviews with gentrifiers from various waves, supported by the analysis of long-term localized statistics, systematically replaced in the global and local contexts, the survey sheds light both on the sociological changes affecting historical central and suburb neighbourhoods and on the reshaping of higher fractions of the middle classes.
