My project investigates the process as well as the structural implications of the decline in the rate of occurrence of finite pronominal enclisis in fifteenth-century Spanish. I will collect and quantitatively analyse data from authentic medieval texts. I will use the R software environment to perform logistic regression analysis and subsequently construct and compare best-fit logistic curves. My research will provide linguists with a more thorough understanding of enclisis and proclisis at all periods of Spanish. Furthermore, given the similarities across Romance, my results could be used in further research by scholars of cliticisation and pertinent systems in related languages.