Selected current research

COVID-19 Vaccination Mandates and Vaccine Uptake (with D. Kim, S. Lu and H. Shigeoka), first draft: Oct. 20, 2021; updated Jan. 10, 2022
Also NBER Working Paper No. 29563, Dec. 2021 and IZA Working Paper No. 14946, Jan. 2022
Keywords: vaccine mandates, vaccine uptake, vaccine hesitancy, proof of vaccination, difference-in-differences, time series, counterfactuals

We evaluate the impact of government-mandated proof of vaccination requirements for access to public venues and non-essential businesses on COVID-19 vaccine uptake. We find that the of a mandate is associated with a rapid and significant surge in new vaccinations (more than 60% increase in weekly first doses), using the variation in the timing of these measures across Canadian provinces in a difference-in-differences approach. Time-series analysis for each province and for France, Italy and Germany corroborates this finding. Counterfactual simulations using our estimates suggest the following cumulative gains in the vaccination rate among the eligible population (age 12 and over) as of October 31, 2021: up to 5 percentage points (p.p.) (90% CI 3.9-5.8) for Canadian provinces, adding up to 979,000 (425,000-1,266,000) first doses in total for Canada (5 to 13 weeks after the provincial mandate announcements), 8 p.p.(4.3-11) for France (16 weeks post-announcement), 12 p.p. (5-15) for Italy (14 weeks post-announcement) and 4.7 p.p. (4.1-5.1) for Germany (11 weeks post-announcement).


Blockchains, Collateral and Financial Contracts, 2022, in progress
Keywords: blockchains, contracts, enforcement, mechanism design, collateral

I map the link between financial contracts and the algorithmic tools and constraints of blockchain technology related to property rights, information, commitment and enforcement. I explore the use of blockchains both as direct conduit of financial contracts in different incomplete market scenarios and also as collateral mechanism for on- and off-blockchain transactions and contracts.

Journal articles

  • Face Masks, Public Policies and Slowing the Spread of COVID-19: Evidence from Canada, Journal of Health Economics 78: 102475, 2021 (with S. Lu, H. Shigeoka, C. Chen and S. Pamplona) [PDF]
    Earlier version: NBER Working Paper No. 27891, Oct. 2020
    Policy and media: [WHO Guidance] [CDC Science Brief] [Government of Canada] [ECDC] [National Post] [Vancouver Sun] [Ottawa Citizen] [New York Post] [MSN] [Yahoo!] [The Telegraph] [Daily Mail] [VoxEU] [SFU News]

    Keywords: COVID-19, face masks, non-pharmaceutical interventions (NPI), event study, counterfactuals
    • Involuntary Entrepreneurship - Evidence from Thai Urban Data, World Development 149: 105706, 2021 (with T. Yindok) [PDF]
      Keywords: entrepreneurship, credit constraints, occupational choice, misallocation
      • Transaction Fee Economics in the Ethereum Blockchain, Economic Inquiry 13025, 2021 (with A. Donmez) [PDF]
        Keywords: blockchain, transaction fees, Ethereum, time series, queueing theory
      • Refereed book chapters

        Working papers and research in progress

        COVID-19 Vaccination Mandates and Vaccine Uptake, pre-print, (with D. Kim, S. Lu and H. Shigeoka)

        We evaluate the impact of government-mandated proof of vaccination requirements for access to public venues and non-essential businesses on COVID-19 vaccine uptake. We find that the of a mandate is associated with a rapid and significant surge in new vaccinations (more than 60% increase in weekly first doses), using the variation in the timing of these measures across Canadian provinces in a difference-in-differences approach. Time-series analysis for each province and for France, Italy and Germany corroborates this finding. Counterfactual simulations using our estimates suggest the following cumulative gains in the vaccination rate among the eligible population (age 12 and over) as of October 31, 2021: up to 5 percentage points (p.p.) (90% CI 3.9-5.8) for Canadian provinces, adding up to 979,000 (425,000-1,266,000) first doses in total for Canada (5 to 13 weeks after the provincial mandate announcements), 8 p.p.(4.3-11) for France (16 weeks post-announcement), 12 p.p. (5-15) for Italy (14 weeks post-announcement) and 4.7 p.p. (4.1-5.1) for Germany (11 weeks post-announcement).


        I map the link between financial contracts and the algorithmic tools and constraints of blockchain technology related to property rights, information, commitment and enforcement. I explore the use of blockchains both as direct conduit of financial contracts in different incomplete market scenarios and also as collateral mechanism for on- and off-blockchain transactions and contracts.


        Distinguishing Across Models of International Capital Flows (with M. Wright), new version coming soon

        We formulate and solve a range of dynamic models of international capital flows and risk sharing with imperfect capital markets. We feature both models of exogenously incomplete markets (debt with tax on borrowing or on capital outflows, non-defaultable debt) and models with endogenously incomplete markets (defaultable debt, limited commitment), as well as the complete markets benchmark. All models share common preferences and technology. We use computational methods based on mechanism design, linear programming, and maximum likelihood to estimate and statistically test across the alternative models of international capital markets. Our methods work with cross-sectional or panel data and allow for measurement error and unobserved heterogeneity. We study which models fit best and also what type of data (income, investment, capital, consumption, or all together) can be used to distinguish across the alternative models. Empirically, we use panel data on GDP, government expenditure, consumption, capital stock and investment per capita for 175 countries in 1993-2002. We find that, overall, the defaultable debt and autarky models fit the data best. The complete markets and limited commitment models are rejected in all estimation runs.


        Economics of Crime Networks (with R. Dastranj and S. Easton), in progress

        We study a network-based model of criminal activity. Agents' payoffs depend on the number and structure of links among them and are determined in a Nash equilibrium of a crime effort supply game. Unlike much of the existing literature that takes network structure as given, we analyze optimal network structures, defined as maximizing aggregate payoff. Using potential functions, we give necessary and sufficient conditions that guarantee the existence and uniqueness of equilibria with non-negativity constraints on effort. These results can be used to identify optimal networks for given cost and benefit parameter configurations drawing on graph theory and using a computational algorithm that searches over all possible non-isomorphic networks of a given size. Our results can be also used to study, via numerical simulations, the effects of alternative crime reducing policies on the network structure and crime level - removing agents, removing links or varying the probability of apprehension.


        Social Insurance and Status (with B. Xia), 2012


        Development Dynamics with Credit Rationing and Occupational Choice, 2005

        The paper presents a stylized general equilibrium model of a developing economy in which the wealth distribution, the interest rate, and the wage rate are endogenous and interact dynamically. A credit market imperfection stemming from limited commitment results in allocative inefficiency due to credit rationing and occupational choice constraints. Credit rationing is shown to persist as the economy develops. The proposed model is shown to match both general empirical regularities pertaining to developing economies and macroeconomic data from Thailand. Furthermore, wealth inequality in this setting may be detrimental for economic development, providing a rationale for redistribution policies.


        This paper provides a step-by-step hands-on introduction to the techniques used in setting up and solving moral hazard programs with lotteries using Matlab. It uses a linear programming approach due to its relative simplicity and the high reliability of the available optimization algorithms.



        Other publications