EXOGENOUS PRODUCTION SHOCKS AND TECHNICAL EFFICIENCY AMONG TRADITIONAL IVORIEN RICE FARMERS

This paper uses a unique panel data set and data envelopment analysis (DEA) to obtain estimates of technical efficiency for 492 traditional rice plots in Côte d'Ivoire. The objective of this paper is to explore the importance of explicitly controlling for exogenous shocks to production in technical efficiency estimation. We show how omission of such variables in highly stochastic production environments can lead to serious inferential errors, with potentially significant policy implications. Conventional DEA estimation of a production frontier, followed by second-stage Tobit estimation of the correlates of plot- level technical efficiency, suggest widespread and substantial inefficiency related to crop fragmentation and seed varieties. However, when one controls for unobserved groupwise cross-sectional and intertemporal heterogeneity and introduces measurable exogenous shocks into the second-stage estimation, managerial characteristics become jointly insignificant and state-conditional technical efficiency becomes nearly universal. The implication is that conventional technical efficiency estimates that refute the classic Schultzian "poor but efficient" hypothesis may be incorrect because they ignore farmers' vulnerability to adverse states of nature against which they cannot insure.Africa (Sub-Saharan), Ivory Coast, production frontiers, agricultural productivity, rice., Crop Production/Industries, Productivity Analysis, O12, Q12, D2,

Workshop on entrepreneurial finance: a summary

This Policy Discussion Paper summarizes papers that were presented at the Workshop on Entrepreneurial Finance, which was held March 12?13, 2009, at the Federal Reserve Bank of Cleveland. Researchers presented new empirical research that exploits data sets on entrepreneurial activity that are based on broad and representative data samples. Papers in the workshop focused primarily on analyses of the sources and structure of start-up finance, including the importance of bank lending, venture capital, angel investors, and owner equity.Small business - Finance

A Bayesian Variable Selection Approach to Major League Baseball Hitting Metrics

Numerous statistics have been proposed for the measure of offensive ability in major league baseball. While some of these measures may offer moderate predictive power in certain situations, it is unclear which simple offensive metrics are the most reliable or consistent. We address this issue with a Bayesian hierarchical model for variable selection to capture which offensive metrics are most predictive within players across time. Our sophisticated methodology allows for full estimation of the posterior distributions for our parameters and automatically adjusts for multiple testing, providing a distinct advantage over alternative approaches. We implement our model on a set of 50 different offensive metrics and discuss our results in the context of comparison to other variable selection techniques. We find that 33/50 metrics demonstrate signal. However, these metrics are highly correlated with one another and related to traditional notions of performance (e.g., plate discipline, power, and ability to make contact)

MACROECONOMIC SHOCKS, HUMAN CAPITAL AND PRODUCTIVE EFFICIENCY: EVIDENCE FROM WEST AFRICAN FARMERS

Little empirical work has quantified the transitory effects of macroeconomic shocks on farm-level production behavior. We develop a simple analytical model to explain how macroeconomic shocks might temporarily divert managerial attention, thereby affecting farm-level productivity, but perhaps to different degrees and for different durations across production units. We then successfully test hypotheses from that model using panel data bracketing massive currency devaluation in the west African nation of Cote d'Ivoire. We find a transitory increase in mean plot-level technical inefficiency among Ivorien rice producers and considerable variation in the magnitude and persistence of this effect, attributable largely to ex ante complexity of operations, and the educational attainment and off-farm employment status of the plot manager.Labor and Human Capital, O1, Q12, Q18,

Hands-on Gravitational Wave Astronomy: Extracting astrophysical information from simulated signals

In this paper we introduce a hands-on activity in which introductory astronomy students act as gravitational wave astronomers by extracting information from simulated gravitational wave signals. The process mimics the way true gravitational wave analysis will be handled by using plots of a pure gravitational wave signal. The students directly measure the properties of the simulated signal, and use these measurements to evaluate standard formulae for astrophysical source parameters. An exercise based on the discussion in this paper has been written and made publicly available online for use in introductory laboratory courses.Comment: 5 pages, 4 figures; submitted to Am. J. Phy

Science Icebreaker Activities: An Example from Gravitational Wave Astronomy

At the beginning of a class or meeting an icebreaker activity is often used to help loosen the group and get everyone talking. Our motivation is to develop activities that serve the purpose of an icebreaker, but are designed to enhance and supplement a science-oriented agenda. The subject of this article is an icebreaker activity related to gravitational wave astronomy. We first describe the unique gravitational wave signals from three distinct sources: monochromatic binaries, merging compact objects, and extreme mass ratio encounters. These signals form the basis of the activity where participants work to match an ideal gravitational wave signal with noisy detector output for each type of source.Comment: Accepted to The Physics Teacher. Original manuscript divided into two papers at the request of the referee. For a related paper on gravitational wave observatories see physics/050920

New light on Galactic post-asymptotic giant branch stars. I. First distance catalogue

We have commenced a detailed analysis of the known sample of Galactic post-asymptotic giant branch (PAGB) objects compiled in the Toru\'n catalogue of Szczerba et al., and present, for the first time, homogeneously derived distance determinations for the 209 likely and 87 possible catalogued PAGB stars from that compilation. Knowing distances are essential in determining meaningful physical characteristics for these sources and this has been difficult to determine for most objects previously. The distances were determined by modelling their spectral energy distributions (SED) with multiple black-body curves, and integrating under the overall fit to determine the total distance-dependent flux. This method works because the luminosity of these central stars is very nearly constant from the tip of the AGB phase to the beginning of the white-dwarf cooling track. This then enables us to use a standard-candle luminosity to estimate the SED distances. For Galactic thin disk PAGB objects, we use three luminosity bins based on typical observational characteristics, ranging between 3500 and 12000 L_sun. We further adopt a default luminosity of 1700 L_sun for all halo PAGB objects. We have also applied the above technique to a further sample of 69 related nebulae not in the current edition of the Toru\'n catalogue. In a follow-up paper we will estimate distances to the subset of RV Tauri variables using empirical period-luminosity relations, and to the R\,CrB stars, allowing a population comparison of these objects with the other subclasses of PAGB stars for the first time.Comment: 24 pages, 8 tables, 4 figures. Submitted to MNRAS. Appendix B containing full list of SED figures excluded in this versio