Kazuatsu Shimizu

I am a PhD candidate in Economics at MIT. My research focuses on international trade and macroeconomics. I am on the 2026–27 job market.

Job Market Paper

The Keynesian Case for Trade Protection: A Modern Treatment

With Keelan Beirne

Working paper

We revisit the Keynesian rationale for tariffs: when downward nominal wage rigidity creates inefficient employment losses, tariffs can serve as second-best instruments by expanding labor demand in affected sectors. We characterize optimal tariffs in a dynamic multisector economy with wage rigidities and a flexible exchange rate. Our contribution is twofold. First, from an analytical standpoint, tariffs can be counterproductive instruments: they may reduce labor demand in the very sectors they are meant to protect, as currency appreciation depresses export demand and discourages current spending. As a result, optimal tariffs may be subsidies. Second, from a quantitative standpoint, optimal interventions and the associated welfare gains remain modest in our U.S. application even when labor distortions are sizable. Optimal tariffs are small because of their limited effectiveness in shifting employment across sectors relative to the distortions they create.

Publications

Task-Based Discrimination

With Erik Hurst and Yona Rubinstein

American Economic Review, 114(6): 1723–1768, 2024.

Published article · Working paper

We develop a task-based model of occupational sorting to identify and quantify the effect of discrimination, racial skill gaps, and aggregate task prices on Black-White differences in labor market outcomes over time. At the heart of our framework is the idea that the size and nature of racial barriers faced by Black workers vary by the task requirements of each job. We define a new task that measures the extent to which individuals interact with others as part of their job. We show that this measure is a good proxy for the extent of discrimination in the economy.

Working Papers

Romer or Ricardo?

With Chang-Tai Hsieh and Peter Klenow

Working paper, 2022; revision in progress.

Working paper

How do new varieties and quality improvements shape trade, growth, and the gains from foreign innovation? We develop a multicountry model combining new variety creation and international technology diffusion. On the theoretical front, we show that foreign growth through new variety creation raises home welfare by creating new sources of comparative advantage, while foreign growth through creative destruction can lower home welfare by eroding home’s comparative advantage and worsening its terms of trade. On the empirical front, we use product-level export and import dynamics to infer countries’ innovation patterns. The estimates suggest that the United States specializes in creating new varieties, while China relies more heavily on improving products developed abroad.

Selected Work in Progress

Trade Protection and Global Value Chains: The Good, the Bad, and the Optimal

With Arnaud Costinot

The Costs of Trade Wars: Theory and Evidence from the Great Depression

With Keelan Beirne

Teaching

MIT Department of Economics

14.581 International Economics I — Graduate
Teaching assistant to Arnaud Costinot and David Atkin, 2024 and 2025.

14.54 International Trade — Undergraduate
Teaching assistant to Arnaud Costinot, 2023–2025.

14.05 Intermediate Macroeconomics — Undergraduate
Teaching assistant to Chris Cotton, 2023.

Best Teaching Assistant Award, MIT Department of Economics, 2024–2025.