ABSTRAeTThis papel' 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 bctween investment and growth rates time series. To characterize the convergence properties and the dynamics of the model we develop analytical and numencaJ rnethods that should be of ¡nterest fOl the general resolution of endogenous growth models with vintage capital. RESUMENEn este artículo se analiza la dinámica de uu modelo de crecimiento endógeno de la clase AK en presencia de cosechas de capital (vintage capital). La inclusión en el modelo de una estructura vintage da lugar a una dinámica oscilatoria, vinculada a lo que se conoce como ecos de reemplazo, los cuales a su vez tienen efectos sobre el nivel de la senda de crecimiento equilibrado. Esta propiedad contrasta marcadamente con el comportamiento del modelo AK estándar, y puede contribuir a explicar las desviaciones a corto plazo, que se observan en los datos, ent.re las tasas de inversión y las tasas de crecimiento. Para caracterizar las propiedades de convergencia y la dinámica del modelo se desarrollan métodos analíticos y numéricos que son de interés para la resolución de modelos de crecimiento endógeno con cosechas de capital.

This paper explores how changes in energy intensity and the switch to renewables can boost economic growth. To do so, we implement a dynamic panel data approach on a sample of 134 countries over the period 1960 to 2010. We incorporate a set of control variables, related to human and physical capital, socio-economic conditions, policies and institutions, which have been widely used in the literature on economic growth. Given the current state of technology, improving energy intensity is growth enhancing at the worldwide level. Moreover, conditional to energy intensity, moving from fossil fuels to frontier renewables (wind, solar, wave or geothermic) is also positively correlated with growth. Our results are robust to the specification of the dynamic panel with respect to alternative approaches (pooled OLS, within group or system GMM), and to alternative specifications (accounting for heterogeneity across countries, a set of institutional factors, and other technical aspects).

This paper presents the model used for simulation purposes within the Spanish Ministry of Economic Affairs and Finance. REMS (a Rational Expectations Model for the Spanish economy) is a small open economy dynamic general equilibrium model in the vein of the New-Neoclassical-Keynesian synthesis models, with a strongly micro-founded system of equations. In the long run REMS behaves in accordance with the neoclassical growth model. In the short run, it incorporates nominal, real and financial frictions. Real frictions include adjustment costs in consumption (via habits in consumption and rule-of-thumb households) and investment into physical capital. Due to financial frictions, there is no perfect arbitrage between different types of assets. The model also allows for slow adjustment in wages and price rigidities, which are specified through a Calvo-type Phillips curve. All these modelling choices are fairly in line with other existing models for the Spanish economy. One valuable contribution of REMS to the renewed vintage of D(S)GE models attempting to feature the Spanish economy is the specification of the labour market according to the search paradigm, which is best suited to assess the impact of welfare policies on both the intensive and extensive margins of employment. The model's most valuable asset is the rigour of the analysis of the transmission channels linking policy action with economic outcomes.

Differential equations with advanced and delayed time arguments may arise in the optimality conditions of simple growth models with delays. Models with investment gestation lags (time-to-build), consumption gestation lags (habit formation) or learning by using lie in this category. In this paper, we propose a shooting method to deal with leads and lags in the Euler system associated to dynamic general equilibrium models in continuous time. We introduce the discussion describing the dynamics that emerge under various assumptions on learning by using and gestation lags. Then, we implement the numerical method we propose to solve for the short run dynamics of a neoclassical growth model with a simple time-to-build lag.