Vintage capital and the dynamics of the AK model

This paper analyzes the equilibrium dynamics of an AK-type endogenous growth model with vintage capital. The inclusion of vintage capital leads to oscillatory dynamics governed by replacement echoes, which additionally influence the intercept of the balanced growth path. These features, which are in sharp contrast to those from the standard AK model, can contribute to explaining the short-run deviations observed between investment and growth rates time series. To characterize the optimal solutions of the model we develop analytical and numerical methods that should be of interest for the general resolution of endogenous growth models with vintage capital.     

The Development Problem under Embodiment

This paper studies technology adoption in an optimal growth model with embodied technical change. The economy consists of the final good sector, the capital sector, and the technology sector which role is the imitation of exogenous innovations. Scarce labor resources are allocated to the technology and final good sectors. The final good is allocated to consumption and to the capital sector. The authors analytically characterize the long run optimal allocations. Using a calibrated version of the model, they find that an acceleration in the rate of embodied technical change should not be responded by an immediate and strong adoption effort. Instead, adoption labor should decrease in the short run, and the optimal technological gap is shown to increase either in the short or in the long run. The state of the institutions and policies around the technology sector is key in the design of the optimal adoption timing.     

Vintage capital and the diffusion of clean technologies

We develop a general equilibrium vintage capital model with energy‐saving technological progress and an explicit energy sector to study the impact of investment subsidies on equilibrium investment and output. Energy and capital are assumed to be complementary in the production process. New machines are less energy‐consuming and scrapping is endogenous. Two polar market structures are considered for the energy market: free entry and natural monopoly. First, it is shown that investment subsidies may induce a larger equilibrium investment into cleaner technologies either under free entry or natural monopoly. However, in the latter case, this happens if and only if the average cost is decreasing fast enough. Second, larger diffusion rates do not necessarily mean lower energy consumption at equilibrium, which may explain certain empirical observations.     

Viable Ramsey economies

The Ramsey model of economic growth is revisited from the perspective of viability theory. The Ramsey model, augmented with minimal consumption and sustainability criteria, becomes a viability problem. The framework allows for a clear picture of optimal viable, optimal non‐viable, and viable non‐optimal paths. The drastic sacrifices in terms of present consumption required by the implementation of Brundtland sustainability are visualized, the rich countries bearing the major part of the burden. The econometric analysis of viability sets enhances the role of technological progress in ensuring Brundtland sustainability. Preference parameters such as the pure time preference rate are statistically non‐significant.     

A closer look at the relationship between life expectancy and economic growth

We first provide a nonparametric inference of the relationship between life expectancy and economic growth using historical data for 18 countries over the period 1820–2005. The obtained shape indicates convexity for low enough values of life expectancy and concavity for large enough values. We then study this relationship using a benchmark model combining "perpetual youth" and learning-by-investing. The generated relationship between life expectancy and economic growth is shown to be strictly increasing and concave. We finally examine two models departing from "perpetual youth" by assuming successively age-dependent earnings and age-dependent survival probabilities. With age-dependent earnings, the obtained relationship is hump-shaped, whereas age-dependent survival laws reproduce the convex–concave shape detected in prior empirical study.     

Embodied Technological Change,Learning‐by‐doing and the Productivity Slowdown*

The productivity slowdown in the US economy since the first oil shock has recently been associated with a larger decline rate of the relative price of equipment investment and a smaller rate of disembodied technical change. We set up a growth model in which learning‐by‐doing is the engine of both embodied and disembodied technological progress. A shift in the relative efficiency of learning‐by‐doing from the consumption to the investment sector is shown to imply a technological reassignment consistent with the above‐mentioned evidence. This result derives from the interaction between the obsolescence costs inherent in embodiment and the learning‐by‐doing engine.     

A Pedagogical Note on Risk Sharing Versus Instability in International Financial Integration: When Obstfeld Meets Stiglitz

Open Economies Review - The pure risk sharing mechanism implies that financial liberalization is growth enhancing for all countries as the world portfolio shifts from safe low-yield capital to...     

Vintage Human Capital, Demographic Trends, and Endogenous Growth

We study how economic growth is affected by demographics in an OLG model with a realistic survival law. Individuals optimally chose the dates at which they leave school to work and at which they retire. Endogenous growth arises thanks to the accumulation of generation-specific human capital. Favorable shifts in the survival probabilities induce longer schooling and later retirement but have an ambiguous effect on per-capita growth. The long-term relationship between fertility and per-capita growth is hump-shaped. Increases in longevity can be responsible for a switch from a no-growth regime to a sustained growth regime and for a positive relationship between fertility and growth to vanish. Solving numerically the equilibrium, demographic changes can have important medium-term effects even if long-term changes are very small. Journal of Economic Literature Classification Numbers: 041, I20, J10.     

CAPITAL MAINTENANCE AS A KEY DEVELOPMENT TOOL

We construct optimal growth models where labor resources can be allocated either to production, technology adoption or capital maintenance. We first characterize the balanced growth paths of a benchmark model without maintenance. Then we introduce maintenance activity via the depreciation rate of capital. We characterize the optimal allocation of labor across the three activities. Although maintenance deepens the technological gap by diverting labor resources from adoption, we show that it generally increases the long run output level. Moreover, we find that equilibrium maintenance and adoption efforts respond in opposite directions to policy or technology shocks. Finally, we find that the long‐term output response to policy shocks is slightly higher in the presence of maintenance.