Gender and party cohesion in the Italian parliament: a spatial analysis

Studies on female legislative behavior suggest that women parliamentarians may challenge party cohesion by allying across party lines. In this paper we analyze a specific parliamentary activity – bill co-sponsorship – in the Italian lower Chamber, between 1979 and 2016, as a source of information about MPs’ original preferences to study how gender affects party cohesion. Do women form a separated group in the Italian parliament? On average, are they more or less distant from the center of their parties than men? Does gender affect systematically party cohesion? A principal component analysis of co-sponsorship data allows us to identify the ideal points of all MPs in a multidimensional space for each legislature. Based on these data we estimate the impact of gender on party cohesion at the individual level while controlling for the impact of several other variables of different kind (individual, partisan, and institutional). We find that: (1) on average, women show lower cohesion as a group inside different parties and higher party cohesion than men; (2) the influence of gender on party cohesion is not conditional upon individual characteristics, upon the size and organization of parliamentary parties, and upon the share of women in their parliamentary groups; (3) the different behavior of women MPs may depend on the different patterns of recruitment in the parties.