Knowledge that Transforms

To explain the rise in Afghan opium production, we explore how rising conflicts change the incentives of farmers. Conflicts make illegal opportunities more profitable as they increase the perceived lawlessness and destroy infrastructure crucial to alternative crops. Exploiting a unique data set, we show that Western hostile casualties, our proxy for conflict, have a strong impact on subsequent local opium production. Using the period after the planting season as a placebo test, we show that conflict has a strong effect before but no effect after planting, indicating causality.

This paper explores the empirical content of the weak axiom of revealed preference (WARP) for repeated cross-sections. In a heterogeneous population, the fraction of consumers who violate WARP is not point identified but can be bounded. These bounds, as well as some nonparametric refinements, correspond to intuitive behavioral assumptions if there are two goods. With three or more goods, such intuitions break down, and plausible assumptions can have counterintuitive implications. We also provide estimators and confidence regions. The empirical application reveals that in the British Family Expenditure Survey, upper bounds are frequently positive but lower bounds are not significantly so.

The Schumpeterian opportunity cost hypothesis predicts that firms concentrate innovative activities in recessions. However, empirical evidence suggests that innovative activities are procyclical. Theory proposes that firms shift R&D investments and innovation from recessions to booms to maximize returns by capturing high-demand periods before imitators compete away rents. This paper provides the first empirical test of these predictions. Results indicate that R&D spending is more procyclical in industries with faster obsolescence, where matching invention to demand is more valuable, and innovation is more procyclical in industries with weaker IP protection, where imitation poses a greater threat.

We investigate the effect of competition on price dispersion in the airline industry. Using panel data from 1993 to 2008, we find a nonmonotonic effect of competition on price dispersion. An increase in competition is associated with greater price dispersion in concentrated markets but with less price dispersion in competitive markets—an inverse-U relationship. Our empirical findings are consistent with an oligopolistic second-degree price discrimination model and encompass contradictory findings in the literature.

This paper examines the productivity growth effects of educational attainment and its interaction with the distance to the world technology frontier, which is the percentage distance to the country with the highest total factor productivity (TFP) (the United Kingdom or United States), while allowing for the endogeneity of educational attainment in some of the estimates. For this purpose, a new annual data set for educational attainment is constructed for 21 industrialized countries over the period from 1870 to 2009. The results show that changes in educational attainment and the interaction between education and the distance to the frontier, as predicted by Schumpeterian growth theory, have been influential for productivity growth over the past 140 years.

Despite the prevalence of R&D support programs, evaluation studies based on explicit differences in support allocation are rare. In this paper, the identification of the causal effect of R&D support on company performance is based on geographic variation in government funding arising from a population-density rule. I find positive impacts on R&D investment, employment, and sales among the participants who were granted an R&D subsidy as a result of additional aggregate R&D support funding in their region. Although there are no instantaneous impacts on productivity, the study provides evidence of long-term productivity gains.

We propose an observation-driven dynamic factor model for mixed-measurement and mixed-frequency panel data. Time series observations may come from a range of families of distributions, be observed at different frequencies, have missing observations, and exhibit common dynamics and cross-sectional dependence due to shared dynamic latent factors. A feature of our model is that the likelihood function is known in closed form. This enables parameter estimation using standard maximum likelihood methods. We adopt the new framework for signal extraction and forecasting of macro, credit, and loss given default risk conditions for U.S. Moody's-rated firms from January 1982 to March 2010.

This paper tests whether upstream R&D cooperation leads to downstream collusion. We show that a sufficient condition for identifying collusive behavior is a decline in the market share of firms participating in research joint ventures (RJVs). Using information from the U.S. National Cooperation Research Act, we estimate a market share equation correcting for the endogeneity of RJV participation and R&D expenditures. We find robust evidence that large networks between direct competitors, created through firms being members in several RJVs at the same time, are conducive to collusive outcomes in the product market that reduce consumer welfare. By contrast, RJVs among noncompetitors are efficiency enhancing.

We study how knowledge about the social network of an individual researcher, as embodied in his coauthor relations, helps us in developing a more accurate prediction of his or her future productivity. We find that incorporating information about coauthor networks leads to a modest improvement in the accuracy of forecasts on individual output, over and above what we can predict based on the knowledge of past individual output. Second, we find that the informativeness of networks dissipates over the lifetime of a researcher's career. This suggests that the signaling content of the network is quantitatively more important than the flow of ideas.

We estimate the extent to which legal and administrative fees prevent liquidity-constrained households from declaring bankruptcy. To do so, we study how the 2001 and 2008 tax rebates affected consumer bankruptcy filings. We exploit the randomized timing of the rebate checks and estimate that the rebates caused a significant short-run increase in consumer bankruptcies in both years, with larger effects in 2008 when the rebates were more generous and more widely distributed. Using hand-collected data from individual bankruptcy petitions, we document that households that filed shortly after receiving their rebate checks had higher average liabilities and liabilities-to-income ratios.