The Environment and Directed Technical Change

66 Pages Posted: 3 Nov 2009 Last revised: 21 Sep 2010

See all articles by Daron Acemoglu

Daron Acemoglu

Massachusetts Institute of Technology (MIT) - Department of Economics; Centre for Economic Policy Research (CEPR); National Bureau of Economic Research (NBER)

Philippe Aghion

College de France and London School of Economics and Political Science, Fellow; Centre for Economic Policy Research (CEPR); National Bureau of Economic Research (NBER)

Leonardo Bursztyn

Harvard University - Department of Economics

David Hémous

University of Zürich

Multiple version iconThere are 3 versions of this paper

Date Written: October 2009

Abstract

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 innovation and production; (ii) optimal policy involves both "carbon taxes" and research subsidies, so that excessive use of carbon taxes is avoided; (iii) delay in intervention is costly: the sooner and the stronger is the policy response, the shorter is the slow growth transition phase; (iv) the use of an exhaustible resource in dirty input production helps the switch to clean innovation under laissez-faire when the two inputs are substitutes. Under reasonable parameter values (corresponding to those used in existing models with exogenous technology) and with sufficient substitutability between inputs, it is optimal to redirect technical change towards clean technologies immediately and optimal environmental regulation need not reduce long-run growth. We also show that in a two-country extension, even though optimal environmental policy involves global policy coordination, when the two inputs are sufficiently substitutable environmental regulation only in the North may be sufficient to avoid a global disaster.

Suggested Citation

Acemoglu, Daron and Aghion, Philippe and Bursztyn, Leonardo and Hemous, David, The Environment and Directed Technical Change (October 2009). NBER Working Paper No. w15451. Available at SSRN: https://ssrn.com/abstract=1498952

Daron Acemoglu (Contact Author)

Massachusetts Institute of Technology (MIT) - Department of Economics ( email )

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Centre for Economic Policy Research (CEPR)

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National Bureau of Economic Research (NBER)

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Philippe Aghion

College de France and London School of Economics and Political Science, Fellow ( email )

London
United Kingdom

Centre for Economic Policy Research (CEPR)

London
United Kingdom

National Bureau of Economic Research (NBER)

1050 Massachusetts Avenue
Cambridge, MA 02138
United States

Leonardo Bursztyn

Harvard University - Department of Economics ( email )

Littauer Center
Cambridge, MA 02138
United States

David Hemous

University of Zürich ( email )

Zürich
Switzerland

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