Japanese Diet Legislative Speech Ideology Estimates 1959-2019

Offering estimated ideological positions of Japanese political parties derived from committee speeches in the Diet from 1959 to 2019. It applies the Wordshoal method and dynamic factor analysis to quantify party stances on specific policy topics and aggregate them into yearly one-dimensional ideal points.

Use Cases

• Estimate longitudinal one-dimensional ideal points for political parties using aggregated yearly scores.
• Analyze changes in party ideological positions over time using the dynamic factor analysis results.
• Identify controversial policy topics from the Wordshoal method's topic-specific position estimates.
• Visualize the axis of conflict in Japanese parliamentary debates based on estimated party positions.

Strengths

• Covers a long temporal range of 60 years (1959-2019).
• Derived from a structured source, the Diet Proceedings Database.
• Applies established quantitative text analysis methods (Wordshoal, dynamic factor analysis).

Limitations

• The underlying text data (committee speeches) is not included, limiting reproducibility of the core estimates.
• Ideal points are aggregated yearly, which may obscure finer-grained temporal dynamics within sessions.
• Methodological reliance on the Wordshoal model's assumptions may influence the ideological dimensions extracted.

Provenance

Source

Diet Proceedings Database.

Collection Method

Quantitative text analysis (Wordshoal method) applied to committee speech transcripts, with yearly aggregation via dynamic factor analysis.

Time Range

1959 to 2019.

Freshness

Data covers up to 2019; metadata was last updated in 2026.

Geography

Japan (specifically the Japanese Diet: House of Representatives and House of Councillors).