Keyword Assisted Topic Models

Shusei Eshima (Harvard University), Tomoya Sasaki (Massachusetts Institute of Technology) and Kosuke Imai (Harvard University)

Abstract: For a long time, many social scientists have conducted content analysis by using their substantive knowledge and manually coding documents. In recent years, however, fully automated content analysis based on probabilistic topic models has become increasingly popular because of their scalability. Unfortunately, applied researchers find that these models often fail to yield topics of their substantive interest by inadvertently creating nonsensical topics or multiple topics with similar content. In this paper, we empirically demonstrate that providing topic models with a small number of keywords can substantially improve their performance. The proposed keyword assisted topic model (keyATM) offers an important advantage that the specification of keywords requires researchers to label topics prior to fitting a model to the data. This contrasts with a widespread practice of post-hoc topic interpretation and adjustments that compromises the objectivity of empirical findings. In our applications, we find that the keyATM provides more interpretable results, has better document classification performance, and is more robust to the number of topics than the standard topic models. Finally, the keyATM can also incorporate covariates and model time trends. An open-source software package is available for implementing the proposed methodology.

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