Measuring Party Ideologies from 30 years of Knesset Plenary Sessions

Party ideologies are latent, elusive dynamic forces that shape democratic competition and representation. Systematically measuring them over time remains a significant challenge. In this paper I develop and validate a novel framework for measuring and positioning the ideologies of parties. My approach uses LLMs for stance detection in the complex yet highly foundational source of parliamentary protocols. The method evaluates domain relevancy per paragraph and then sentence stances towards policies (MARPOR project's 56 categories), while considering preceding remarks as relevant context and controlling for political cues. I demonstrate the framework’s value by applying it to the plenary sessions of the Israeli Knesset throughout 1999-2022. For the first time, I offer quantitative, empirical ground for studying changes in the ideologies promoted by Israeli parties. I aggregate the results into multiple ideological axes, and explore the impact of significant historical events on the ideologies and policies promoted by parties.