The Making of International Tax Law Empirical Evidence from Tax Treaties Text

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Elliott Ash
Omri Marian


We offer the first attempt at empirically testing the level of transnational consensus on the legal language controlling international tax matters. We also investigate the institutional framework of such consensus-building. We build a dataset of 4,052 bilateral income tax treaties, as well as 16 model tax treaties published by the United Nations (U.N.), Organisation for Economic Co-operation and Development (OECD), and the United States. We use natural language processing to perform pair-wise comparison of all treaties in effect at any given year. We identify clear trends of convergence of legal language in bilateral tax treaties since the 1960s, particularly on the taxation of cross-border business income. To explore the institutional source of such consensus, we compare all treaties in effect for any given year to the model treaties in effect during that year. We also explore whether recently concluded treaties converge towards legal language in newly introduced models. We find the OECD Model Tax Convention (OECD Model) to have a significant influence. The years following the adoption of a new OECD Model show a clear trend of convergence in newly adopted bilateral tax treaties towards the language of the new OECD Model. We also find that model treaties published by the U.N. (U.N. Model) have little immediate observable effect, though U.N. treaty policies seem to have a delayed, yet lasting effect. These findings portray the OECD as the institutional source of legal drafting on international tax matters. The normative implications of these findings, however, are not obvious. We offer several normative interpretations for our findings.

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Author Biographies

Elliott Ash, ETH Zurich

Assistant Professor of Law, Economics, and Data Science, ETH Zurich (ashe@ethz .ch).

Omri Marian, University of California, Irvine

Professor of Law and Academic Director of the Graduate Tax Program, University of California, Irvine, School of Law ( Joey O’Brien, Dion Dierdtich, and Sarah Laabid provided excellent research assistance.