We construct a dynamic integrated assessment model of climate and the economy with very high geographic resolution. Migration is free within, but not allowed across, countries. The model parameterization uses a wealth of data, including the distribution of output, population, energy sources and use, and estimates of the local damages from climate change. It implies very large geographic dispersion in damages from warming. We conduct three kinds of policy experiments. In one, we note that a modest, uniform carbon tax limits global warming and damages around the world substantially. In a second experiment, we let the poorest countries not tax carbon, while the rest compensate by setting higher taxes; the efficiency losses are large. In a final experiment, we find that fast green technology growth alone is a poor substitute for carbon taxes, whether globally available or not.

The role that investment-specific technological change played in generating post-war U.S. growth is investigated here. The premise is that the introduction of new, more efficient capital goods is an important source of productivity change, and an attempt is made to disentangle its effects from the more traditional Hicks-neutral form of technological progress. The balanced growth path for the model is characterized and calibrated to U.S. National Income and Product Account (NIPA) data. The quantitative analysis suggests that investment-specific technological change accounts for the major part of growth.

We study a positive theory of stagnation and growth aimed at understanding the large variations in growth outcomes across actual economies. The theory points to the fundamental role played by vested interests in determining policies which are key to the growth process: some agents seek to prevent the adoption of new technologies. We develop a model of technology adoption, and show how technological innovation may sow the seeds of its own destruction. In particular, we find that the equilibrium is characterized by a long cycle of stagnation and growth. Over this cycle, incumbent innovators have sufficient political influence that new technologies are prohibited, and only as these incumbents are phased out of the economy will new innovation occur. In formalizing our theory we make a methodological contribution by characterizing dynamic voting equilibria in which voters must forecast the effects of different current policies on future prices and policy outcomes.

Thomas Piketty’s recent book Capital in the Twenty-First Century is a timely and important contribution that turns our attention to striking long-run trends in economic inequality. A large part of the book is thus a documentation of historical data, going further back in time, and focusing more on the very richest in society, than have most existing economic

Does capital-embodied technological change play an important role in shaping labour-market outcomes? To address this question, we develop a model with vintage capital and search-matching frictions where irreversible investment in new vintages of capital creates heterogeneity in productivity among firms, matched as well as vacant. We demonstrate that capital-embodied technological change reduces labour demand and raises equilibrium unemployment and unemployment durations. In addition, the presence of labour-market regulations (unemployment benefits, payroll taxes, and firing costs) exacerbates these effects. Thus, the model is qualitatively consistent with some key features of the European labour-market experience relative to that of the U.S.: it features a sharper rise in unemployment and a sharper fall in the vacancy rate and the labour share. A calibrated version of our model suggests that this technology—policy interaction could explain a sizeable fraction of the observed differences between the U.S. and Europe.

This paper takes as given that (i) the burning of fossil fuel increases the carbon dioxide content in the atmosphere, which (ii) in turn leads to global heating and global climate change of a

We study a dynamic version of Meltzer and Richard's median-voter model of the size of government. Taxes are proportional to total income, and they are redistributed as equal lump-sum transfers. Voting takes place periodically over time, and each consumer votes for the tax rate that maximizes his equilibrium utility. We calibrate the model to U.S. data. Key elements in the calibration are the income and wealth distribution and the parameters governing the leisure and consumption choices. The total size of transfers predicted by our political-economy model is quite close to the size of transfers in the data.

We study optimal taxation when consumers have temptation and self-control problems. Embedding the class of preferences developed by Gul and Pesendorfer into a standard macroeconomic setting, we first prove, in a two-period model, that the optimal policy is to subsidize savings when consumers are tempted by “excessive” impatience. The savings subsidy improves welfare because it makes succumbing to temptation less attractive. We then study an economy with a long but finite horizon which nests, as a special case, the Phelps–Pollak–Laibson multiple-selves model (thereby providing guidance on how to evaluate welfare in this model). We prove that when period utility is logarithmic, the optimal savings subsidies increase over time for any finite horizon. Moreover, as the horizon grows large, the optimal policy prescribes a constant subsidy, in contrast to the well known Chamley–Judd result.

We develop a quantitative macroeconomic theory of input-saving technical change to analyze how markets economize on scarce natural resources, with an application to fossil fuel. We find that aggregate US data call for a very low short-run substitution elasticity between energy and the capital/labor inputs. Our estimates imply that energy-saving technical change took off when the oil shocks hit in the 1970s. This response implies significant substitutability with the other inputs in the long run: even under ever-rising energy prices, long-run consumption growth is still possible, along with a modest factor share of energy.