I focus mainly on knowledge, innovation, and economic growth. In particular, I study how knowledge is accumulated and diffused, how innovation occurs at the individual and firm level, and how these map into outcomes at a societal level.
Publications (click for abstract)
Assessing the Rate of Replication in Economics, American Economic Review (Papers and Proceedings), 2017 (with James Berry, Lucas Coffman, Rania Gihleb, and Alistair Wilson)
We assess the rate of replication for empirical papers in the 2010 American Economic Review. Across seventy empirical papers, we find that 29 percent have one or more citation that partially replicates the original result. While only a minority of papers has a published replication, a majority (sixty percent) have either a replication, robustness test or an extension. Surveying authors within the literature we find substantial uncertainty over the number of extant replications.
Transition to Clean Technology, Journal of Political Economy, 2016 (with Daron Acemoglu, Ufuk Akcigit, and William Kerr)
We develop an endogenous growth model where clean and dirty technologies compete in production. Research can be directed to either technology. If dirty technologies are more advanced, the transition to clean technology can be difficult. Carbon taxes and research subsidies may encourage production and innovation in clean technologies, though the transition will typically be slow. We estimate the model using microdata from the US energy sector. We then characterize the optimal policy path which heavily relies on both subsidies and taxes. Finally we evaluate various alternative policies. Relying only on carbon taxes or delaying intervention have significant welfare costs.
Working Papers (click for abstract)
Innovation and Patent Policy with Interdependent Technology
There is substantial heterogeneity across industries in the level of interdependence between new and old technologies. I propose a measure of this interdependence—an index of sequentiality in innovation—which is the transfer rate of patents in a particular industry. I find that highly sequential industries have higher profitability, higher variance of firm growth, lower exit rates, and lower rates of patent expiry. To better understand these trends, I construct a model of firm dynamics where the productivity of firms evolves endogenously through innovations. New innovators either replace existing technologies or must purchase the rights to existing technologies from incumbents in order to produce, depending on the level of sequentiality in the industry. Estimating the model using data on US firms and recent data on US patent transfers, I can account for a large fraction of the cross-industry trends described above. Because innovation results in larger monopoly distortions in more sequential industries, there is an overinvestment of research inputs into these industries. This misallocation, which amounts to 2.5% in consumption equivalent terms, can be partially remedied using a patent policy featuring weaker protection in more sequential industries, producing welfare gains of 1.7%.
Optimal Taxation and R&D Policies, NBER Working Paper 22908 (with Ufuk Akcigit and Stefanie Stantcheva)
We study the optimal design of R&D policies and corporate taxation when the outputs of innovation are not appropriable in the absence of intellectual property rights policies and there are non-internalized technology spillovers across firms. Firms are heterogeneous in their research productivity, i.e., in the efficiency with which they convert a given set of R&D inputs into successful innovations. There is asymmetric information about firm productivity and about its stochastic evolution over time that prevents the first best solution to the technology spillover. The problem is thus posed as one of dynamic mechanism design with externalities. We characterize the optimal constrained efficient allocations over firms' life cycles and for firms of different productivities. We show that the constrained efficient allocations can be implemented either by a patent system plus a price subsidy for the monopolists' products, together with a parsimonious R&D subsidy function or, equivalently, by a prize mechanism. We estimate our model using firm-level data matched to patent data and quantify the optimal policies. Simpler innovation policies, such as linear R&D subsidies and linear profit taxes, lead to large revenue losses relative to the optimal mechanism.
Back to Basics: Basic Research Spillovers, Innovation Policy and Growth, CEPR Discussion Paper 11707 (with Ufuk Akcigit and Nicolas Serrano-Velarde) cited in the Economic Report of the President 2016
This paper introduces a general equilibrium model of endogenous technical change through basic and applied research. Basic research differs from applied research in the nature and the magnitude of the generated spillovers. We propose a novel way of empirically identifying these spillovers and embed them in a framework with private firms and a public research sector. After characterizing the equilibrium, we estimate our model using micro-level data on research expenditures by French firms. Our key finding is that standard innovation policies (e.g., uniform R&D tax credits) can accentuate the dynamic misallocation in the economy by oversubsidizing applied research. Policies geared towards public basic research and its transmission to the private sector are significantly welfare improving.
Work in Progress
The Effect of Wikipedia on Scientific Progress (with Neil Thompson)
International Competition in the Race to Clean Technology (with Chengying Luo)
Yellow Fever and the Growth of American Cities (with Sean McCoy and Werner Troesken)
Firm Clustering Using Machine Learning (with Tamara Broderick, Trevor Campbell, Jeffrey Kuhn, and Neil Thompson)
First off, check out my GitHub page! There you can find code relating to the above papers, the below listed projects, and other side projects.
Stuck in LaTeX/PDF hell? There may be a way out. Nowadays, academics are relying less and less on the printed page. At the same time, there have been major advances in the speed and functionality of web technology, particularly in the mobile space. Check out the live demo above!
I aim to produce a framework that can supplant LaTeX as the major tool for the promulgation of academic research. The benefits of such a framework will come both in the form of ease of use (for both the producer and consumer) and in an increased ability to integrate with existing web technologies.
Below is a service that allows you to look at the cumulative relative editing activity for a large number of tokens (about 1.1M) appearing in Wikipedia. You can type in your own (single) words into the box below, separated by commas, and see the results by pressing enter. You can also download the results in CSV form by clicking the button.
In this project, I'm attempting to develop a framework for easy-to-use, real-time web plotting. The primary use case is for dashboards that display information on running calculations, but others are of course possible. The backend uses WebSockets and Tornado to interface with MATLAB/Matplotlib-style plotting commands. The frontend uses d3.js.
Advances in computing are critical for expanding the set of models that we can feasibly investigate quantitatively. GPU's are highly parallelized processing units, originally designed for use in video games, but increasingly finding their way into high performance computing. I gave a lecture in 2011 at Penn detailing how economists might use these in their research. The field is of course evolving rapidly on both the hardware and software fronts, so this may not incorporate all recent changes.