David Hemous

University of Zurich
Schönberggasse 1
8001 Zürich, Switzerland


NBER Working Papers and Publications

June 2015Innovation and Top Income Inequality
with Philippe Aghion, Ufuk Akcigit, Antonin Bergeaud, Richard Blundell: w21247
In this paper we use cross-state panel data to show a positive and significant correlation between various measures of innovativeness and top income inequality in the United States over the past decades. Two distinct instrumentation strategies suggest that this correlation (partly) reflects a causality from innovativeness to top income inequality, and the effect is significant: for example, when measured by the number of patent per capita, innovativeness accounts on average across US states for around 17% of the total increase in the top 1% income share between 1975 and 2010. Yet, innovation does not appear to increase other measures of inequality which do not focus on top incomes. Next, we show that the positive effects of innovation on the top 1% income share are dampened in states with ...
December 2012Carbon Taxes, Path Dependency and Directed Technical Change: Evidence from the Auto Industry
with Philippe Aghion, Antoine Dechezleprêtre, Ralf Martin, John Van Reenen: w18596
Can directed technical change be used to combat climate change? We construct new firm-level panel data on auto industry innovation distinguishing between "dirty" (internal combustion engine) and "clean" (e.g. electric and hybrid) patents across 80 countries over several decades. We show that firms tend to innovate relatively more in clean technologies when they face higher tax-inclusive fuel prices. Furthermore, there is path dependence in the type of innovation both from aggregate spillovers and from the firm's own innovation history. Using our model we simulate the increases in carbon taxes needed to allow clean to overtake dirty technologies.

Published: Philippe Aghion & Antoine Dechezlepr�tre & David H�mous & Ralf Martin & John Van Reenen, 2016. "Carbon Taxes, Path Dependency, and Directed Technical Change: Evidence from the Auto Industry," Journal of Political Economy, University of Chicago Press, vol. 124(1), pages 000 - 000. citation courtesy of

October 2009The Environment and Directed Technical Change
with Daron Acemoglu, Philippe Aghion, Leonardo Bursztyn: w15451
This paper introduces endogenous and directed technical change in a growth model with environmental constraints and limited resources. A unique final good is produced by combining inputs from two sectors. One of these sectors uses "dirty" machines and thus creates environmental degradation. Research can be directed to improving the technology of machines in either sector. We characterize dynamic tax policies that achieve sustainable growth or maximize intertemporal welfare, as a function of the degree of substitutability between clean and dirty inputs, environmental and resource stocks, and cross-country technological spillovers. We show that: (i) in the case where the inputs are sufficiently substitutable, sustainable long-run growth can be achieved with temporary taxation of dirty innova...

Published: Daron Acemoglu & Philippe Aghion & Leonardo Bursztyn & David Hemous, 2012. "The Environment and Directed Technical Change," American Economic Review, American Economic Association, vol. 102(1), pages 131-66, February. citation courtesy of

June 2009Credit Constraints, Cyclical Fiscal Policy and Industry Growth
with Philippe Aghion, Enisse Kharroubi: w15119
This paper evaluates whether the cyclical pattern of fiscal policy can affect growth. We first build a simple endogenous growth model where entrepreneurs can invest either in short-run projects or in long-term growth enhancing projects. Long-term projects involve a liquidity risk which credit constrained firms try to overcome by borrowing on the basis of their short-run profits. By increasing firms' market size in recessions, a countercyclical fiscal policy will boost investment in productivity-enhancing long-term projects, and the more so in sectors that rely more on external financing or which display lower asset tangibility. Second, the paper tests this prediction using Rajan and Zingales (1998)'s diff-and-diff methodology on a panel data sample of manufacturing industries across 17 OEC...

Published: Cyclical fiscal policy, credit constraints, and industry growth ☆ Philippe Aghiona, David Hemousa, Enisse Kharroubib, Journal of Monetary Economics Available online 29 January 2014

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