Quantitative Analysis of Post-War Japanese Prime Ministers' Diet Speeches

Abstract

　In this study, we conducted text mining on the Diet speeches (both administrative policy speech and prime minister's general policy speech) of post-war Japanese prime ministers to clarify the chronological changes in political thoughts. A total of 179 speeches from the Higashikuni-no-miya Cabinet (1945) to the fourth Abe Cabinet (2019) were collected, and morphological analysis was performed after dividing them into four periods: the rst half and latter half of the Showa era, and the rst half and latter half of the Heisei era. Characteristic words were extracted by calculating TF-IDF values for frequent nouns in each era. Then, a topic model using LDA was created for all speeches, and topics were estimated for each prime minister.