July 6, 1999 <p> Research and development (R&D) is a key determinant of long run productivity and welfare. A central issue is whether a decentralized economy undertakes too little or too much R&D. We develop an endogenous growth model that incorporates parametrically four important distortions to...</p>

February 26, 1996, Version 5.00 <p> Empirical research in the micro productivity literature consistently supports the notion that there is too little R&D. However, the methodology of this literature, based on the neoclassical growth model, is challenged by new growth theory, which emphasizes a...</p>

December 3, 1998 -- Version 4.0 <p> All growth models are linear in some sense, and the endogenous growth literature can be read as the search for the appropriate linear differential equation. Linearity is a "crucial" assumption, in the sense used by Solow (1956), and it therefore seems reasonable...</p>

September 28, 1999 -- Version 2.0 <p> This paper studies a growth model that is able to match several key facts of economic history. For thousands of years, the average standard of living seems to have risen very little, despite increases in the level of technology and large increases in the level...</p>

January 24, 1997, Version 2.00 <p> Is there too much or too little private research and development (R&D)? A large empirical literature reports estimates of the rate of return to R&D ranging from 30% to over 100%, supporting the notion that there is too little private investment in research....</p>

December 15, 1998 -- Version 1.0 <p> The property that ideas are nonrivalrous leads to a tight link between idea-based growth models and increasing returns to scale. In particular, changes in the size of an economy's population generally affect either the long-run growth rate or the long-run level...</p>

September 26, 1996 -- Version 4.00 <p>The recent literature on convergence has departed from the earlier literature by focusing on the shape of the production function and the rate at which an economy converges to its own steady state. This paper uses advances from the recent literature to look...</p>