Job Market Paper

Why Firms Buy: Dynamic Games of Acquisition Among Tech Giants

Information and technology markets often feature high market concentration and frequent acquisitions. Understanding the motives underlying these acquisition strategies is therefore a first-order question for policy makers and practitioners. Using a dynamic model, I analyze acquisition records of the "big five" (or "tech giants") -- Google, Amazon, Microsoft, Meta, and Apple. I characterize the firms' acquisition decisions observed in the data as a Markov perfect equilibrium that is driven by their scale economies and competitive motive. I find that the motive to keep up with their rivals can explain a major share of their acquisition behaviors, sometimes overshadowing their internal motives of scale economies. I show that a company might opt to acquire not necessarily because it can benefit from technological synergies generated from accumulating similar targets, but to align with the trajectories of their rivals to mitigate the risk of falling behind.


Price and Output Elasticities of Energy Demand for Industrial Sectors in OECD Countries

Boyoon Chang, Sung Jin Kang, and Tae Yong Jung

Sustainability 2019, 11(6), 1786;

The price and output elasticities of energy demand continue to be of interest to academia and policy institutions, having been estimated in previous studies. However, the estimated results show some inconsistencies, especially at the sectoral level, across countries. Based on our conjecture that those inconsistencies are mainly due to the effect of contingent energy intensities and partially to different units of analysis, we narrowed the analysis to the industry level and classified 16 industries into energy-intensive and less energy-intensive groups. The effects of price and output on energy demand were then compared between these two groups using 274 industry panel data across 20 Organization for Economic Cooperation and Development (OECD) countries from 1978 to 2013. The results showed that the price elasticity of energy demand was consistently lower in the energy-intensive group than in the less energy-intensive group, whereas the output elasticity of energy demand was higher in the energy-intensive group than in the less energy-intensive group. Using panel differences and system generalized method of moments estimations, the dynamic elasticities of energy demand were also estimated. Energy demand in reaction to both price and output changes appeared to be more elastic in the long term than in the short term for both energy-intensive and less energy-intensive groups. These findings could be a useful reference for policy makers to deploy separate energy policies for different industries aiming for different temporal effects.

Working Papers

The Short-run Effects of Opening Mobile In-App Payment Systems: Evidence from South Korea

Boyoon Chang and Keaton Miller

Mobile app platforms are highly concentrated - Apple and Google each distribute over 75% of the total number of apps installed on the relevant devices. These platforms generally require developers to use a built-in system for processing payments at a tax rate of 30% for both the initial purchase of an app and any subsequent in-app purchases. In September 2021, South Korea became the first country to ban this lock-in; purchases made in the country may be conducted through any billing system developers wish. We analyze the impact of this policy change on demand for apps and revenue using difference-in-differences techniques and data from a leading app analytics firm from January 2018 to February 2022. We find limited evidence to support the hypotheses that opening in-app payment systems leads to more revenue for developers though fewer downloads.

New draft with updated data coming soon.

Work in Progress

[1] Commission Rate and Platform Competition
[2] Strategic Portfolio Optimization: Balancing Economies of Scope and Economies of Scale in Acquisitions