Public Media Do Serve the State: A Field Experiment

48 Pages Posted: 18 Nov 2019 Last revised: 13 Jan 2020

Date Written: January 12, 2020


A vital role of public media according to the theoretical literature is to enable consumers to cross-check the information provided by slanted private media. To check the neutrality of public media, we conducted a randomized field experiment in Japan in collaboration with the nation's public service broadcaster in which the capacity for viewing its programs was randomly increased. Contrary to our expectations, we find that the treatment increased the evaluation of certain policies by raising the viewing time of its programs. To study the mechanism, we use unsupervised machine learning to measure media slant using the semantic similarity between TV programs and the official statements. Using this metric, we find that the positive effect is driven by subjects’ exposure to information slanted in favor of the domestic government during the experiment. These findings highlight the importance of creating institutions that secure the independence of public media.

Keywords: public media, persuasion, field experiment, machine learning, natural language processing

JEL Classification: K23, L82, D78

Suggested Citation

Kitamura, Shuhei and Kuroda, Toshifumi, Public Media Do Serve the State: A Field Experiment (January 12, 2020). Available at SSRN: or

Toshifumi Kuroda

Tokyo Keizai University

1-7-34, Minami-cho, Kokubunji-shi,
Tokyo, Tokyo 185-8502


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