Measuring Welfare Gains from Online Stores: Theory and Evidence from the Supreme Court's Wayfair Decision
with Yang Su, Job Market Paper
We study how the rise of e-commerce has reshaped consumer welfare and its distributional implications in the presence of retail oligopoly. Based on new data on shopping receipts, we document consumer heterogeneity in online retailing markets: households living in rural areas and with higher incomes are more likely to shop online. To quantify the welfare effects, we leverage an exogenous tax shock by the Supreme Court's Wayfair Decision to learn about online store substitutability and firm pricing responses. We then develop and estimate a structural demand and supply model focussing on the pet food retail market. The model allows us to decompose the consumer online welfare gains into gains from varieties (9%) and convenience (5%) and gains from pro-competitive effects (3%). We further characterize the distributional effects of the rise of e-commerce and find it has reduced consumption inequality between rural and urban areas but increased consumption inequality between the rich and the poor.
The Economics of Traveling:
A Study of High-Speed Railway Expansion
Human mobility across cities is a crucial factor for regional development, yet its effects and mechanism remain poorly understood due to limited data on travel flows and their mixed purposes. This paper addresses this gap by using high-frequency GPS data from mobile users in China to measure travel flows across cities and to disentangle business and leisure activities, which have different implications for regional structural change. Furthermore, I develop a multi-sector economic geography model with both trade in goods and travel in humans to examine the welfare effects of China's recent expansion of the High-Speed-Railway system (HSR) since HSR only reduces people's travel costs, not goods' trade costs. The model suggests travel flows and their sensitivity to spatial functions are sufficient to evaluate welfare. I estimate the human mobility aspect of infrastructural improvement contributes to 0.3 percent of GDP. I also find significant inequality in the gains of HSR across cities and industries. These results have important implications for the ongoing policy debate on infrastructure improvement.
Ecommerce and the Retail Apocalypse
The location of retail establishments in space is a critical decision for firms in the retail market. The rise of e-commerce in recent years has led to the displacement of many offline stores, but the precise mechanisms by which this affects the equilibrium number of stores are not well understood. In this paper, I investigate the direct effect of the rise of e-commerce on the closure of retail branches, as well as its indirect propagation through agglomeration and congestion forces within the retail landscape. To do so, I develop a demand and supply model that accounts for spillovers and unifies various agglomeration and congestion forces discussed in the literature. By examining variations in retailers' exposure to online competition, I disentangle the spillover forces affecting demand and supply. My estimation results demonstrate that agglomeration and congestion forces both exist and are of comparable quantitative importance. Moreover, I show that by combining observed data with spillover parameters, we can separate the direct and indirect effects of e-commerce on the equilibrium store landscape. I analyze the welfare implications of this shift for both consumer welfare and retailer surplus.