Knowledge that Transforms

We develop a parsimonious model of innovation to confront firm‐level evidence. It captures the dynamics of individual heterogeneous firms, describes the behavior of an industry with firm entry and exit, and delivers a general equilibrium model of technological change. While unifying the theoretical analysis of firms, industries, and the aggregate economy, the model yields insights into empirical work on innovating firms. It accounts for the persistence of firms’ R&D investment, the concentration of R&D among incumbents, the link between R&D and patenting, and why R&D as a fraction of revenues is positively correlated with firm productivity but not with firm size or growth.

When markets are incomplete, individuals may choose to marry to diversify their labor income risk. Love, however, can complicate the picture. If love is fleeting or the resolution of agents’ income uncertainty occurs predominantly later in life, then marriages with good economic matches last longer. In contrast, if love is persistent and the resolution of uncertainty to agents’ income occurs early, then marriages with good economic matches are more likely to be caught short with too little love to save a marriage. Consequently, once married, the partners will be more likely to divorce. Evidence is provided to distinguish between these alternative scenarios.

This paper is a theoretical study of rural‐urban migration—urbanization—as it has occurred in many low‐income economies in the postwar period. This process is viewed as a transfer of labor from a traditional, land‐intensive technology to a human capital–intensive technology with an unending potential for growth. The model emphasizes the role of cities as places in which new immigrants can accumulate the skills required by modern production technologies.

Egalement paru dans : Document de travail du LEA ; 02-02 et INRA ESR Toulouse Cahier de Recherche ; 2002-01

We study a general equilibrium model in which entrepreneurs finance investment with optimal financial contracts. Because of enforceability problems, contracts are constrained efficient. We show that limited enforceability amplifies the impact of technological innovations on aggregate output. This implies that economies with lower enforceability of contracts are characterized by greater macroeconomic volatility. A key assumption for the amplification result is that defaulting entrepreneurs are not excluded from the market.

We derive a parsimonious rational model of active portfolio management that reproduces many regularities widely regarded as anomalous. Fund flows rationally respond to past performance in the model even though performance is not persistent and investments with active managers do not outperform passive benchmarks on average. The lack of persistence in returns does not imply that differential ability across managers is nonexistent or unrewarded or that gathering information about performance is socially wasteful. The model can quantitatively reproduce many salient features in the data. The flow-performance relationship is consistent with high average levels of skills and considerable heterogeneity across managers. One of the central mysteries facing financial economics is why financial intermediaries appear to be so highly rewarded, despite the apparent fierce competition between them and the uncertainty about whether