Sangdong Kim (김상동)

Work in Progress

• "Public Debt and Foreign Investment in Aging Developed Economies"
  Job Market Paper | Paper Abstract
  I evaluate a strategy for managing public debt by issuing additional domestic bonds, with yields depressed by population aging and demographic transition, to fund higher-return foreign asset accumulation. I develop an overlapping-generations model with incomplete markets and a rich fiscal structure to analyze the strategy's implications for debt sustainability, macroeconomic outcomes, and welfare. I calibrate the model to the experience of Japan since the mid-1990s. I identify an intertemporal trade-off. In the short run, the policy requires significant increase in debt-to-GDP ratio, which crowds out investment and depresses wages and growth. However, the long-term accumulation of high-yielding foreign assets improves the fiscal outlook, leading to a lower eventual debt-to-GDP ratio and greater capital deepening. The Japanese government's strategy was welfare-improving from a utilitarian perspective with unequal impacts across cohorts. Finally, I show that investing abroad can relax the well-known $r < g$ condition for public debt sustainability.
• "Granular Search in Monopsonistic Labor Market"
  with Sean McCrary | Draft coming soon! Abstract
  We develop a model of monopsonistic labor markets with the granular search protocol, à la Jarosch, Nimczik and Sorkin (2024), where the firm size distribution is endogenously determined. We introduce a simple static model to show that the monopsonist’s effective Nash bargaining power is endogenously determined by the firm’s relative size. Monopsonistic firms choose the optimal vacancy postings taking into account the wage determination, ending up with overposting vacancies to suppress wages.
• "Sovereign Partial Default in Continuous Time"
  with Gabriel Mihalache | Paper Abstract
  We formulate and solve a tractable, continuous time version of the sovereign partial default model of Arellano, Mateos-Planas and Ríos-Rull (2023). We compute our model using both traditional continuous time methods and, with an eye towards larger state space applications, on a deep neural network. We show that our formulation allows for a tight characterization of debt and default dynamics, as well as the length and severity of crisis events.

Pre-doctoral Work

• "The impact of international patenting on corporate patenting activities: Evidence from Korea"
  with Jihong Lee | Technovation, 130, 2024 Abstract
  This paper studies the impact of international patenting on corporate patenting activities, using a novel firm-level dataset from Korea. After making an overseas patent application for the first time, firms increase their overall patenting activity, both domestically and internationally, relative to similar firms that operate only in the domestic market for ideas.
• "Korea Patent Data Project (KoPDP): Contents and Methods"
  with Jihong Lee, Hyunkyeong Lim, Keunsang Song and Jae Yu Jung | The Korean Economic Forum, 2020 Abstract
  In this paper, we describe the contents and methods of “Korea Patent Data Project (KoPDP)”. The project collects all utility patents granted from the Korea Intellectual Property Office (KIPO) for the period 1948-2016 and the US Patent and Trademark Office (USPTO) for the period 1976-2017.

  Replication Data (Harvard Dataverse)