This paper advocates for a greater emphasis on theoretical drivers in the operationalizations of gentrification in empirical studies. In the context of supply sided concepts, this can be achieved by focusing on the transmission channels between drivers and socio-spatial outcomes, particularly through the rental market. Linking insights from the gentrification, price index and hedonic regression literature, this paper seeks to provide a novel framework capable of quantifying neighbourhood level rent gap closings via index construction. It relies solely on listing data and is therefore reproducible in most urban settings. Nonetheless, it is also highly adaptable to a variety of regulatory contexts and other housing market idiosyncrasies through the design of the underlying hedonic regression model. Drawing on data from the city of Vienna, local rent changes and their relationship to housing supply upgrades are quantified. After computing the respective indices, bivariate mapping is utilised to identify potential gentrification areas.