The Law of the Minimum and Sources of Nonzero Skewness for Crop Yield Distributions

Crop yields are not commonly found to be normally distributed, but the cause of the non-normal distribution is unclear. The non-normality might be due to weather variables and/or an underlying von Liebig law of the minimum (LoM) production function. Our objective is to determine the degree to which an underlying linear response stochastic plateau production function can explain the skewness of Oklahoma wheat yields at varied nitrogen rates. We use farm-level wheat data from a long-term experiment in Oklahoma, which is a unique data set to the literature. The Tembo et al. (2008) production function provides negative skewness at all levels of nitrogen with skewness near zero for both very high and very low levels of nitrogen. Observed skewness for wheat yields, however, is positive. The variation in the plateau by year shows positive skewness. Skewness in yield potential related to weather should be considered as a possible explanation of skewness.linear plateau model, non-normal distributions, skewness, wheat, yield distribution, Production Economics, Risk and Uncertainty, Q10,

Micheline Cariño, Aurora Breceda, Antonio Ortega, y Lorella Castorena, coords., Evocando al edén. Conocimiento, valoración y problemática del Oasis de los Comondú. México: Conacyt; Barcelona: Icaria, 2013.

Micheline Cariño, Aurora Breceda, Antonio Ortega, y Lorella Castorena, coords., Evocando al edén. Conocimiento, valoración y problemática del Oasis de los Comondú. México: Conacyt; Barcelona: Icaria, 2013

Agent-based common value auctions

Scope and Method of Study: This research is composed of three essays about agent-based common value auctions. The objective of the first essay is to establish an agent-based first-price common-value auction to determine the impact of a reserve price with two buyers and with three buyers. In the second essay, the agent-based common-value auction model is used to provide theoretical insight into the likely change in beef packers' market power before and after the Livestock Mandatory Price Reporting Act. The objective in the third essay is to determine if a first-price common-value auction with a reserve price or a posted-price market provides a seller with the larger expected revenue using agent-based models. In these three essays several theoretical contributions are made to the auction literature, and developing an agent-based common-value auction extends the agent-based modeling literature.Findings and Conclusions: Results from these essays provide unique insight into auction theory, agent-based modeling, and federal agricultural policy. From the first essay, a reserve price increases the equilibrium winning bid price and decreases the probability that the item is sold in the two and three buyer auctions. Additionally, a reserve price increases the winning bid price more than an additional buyer and no reserve price. In the second essay, results provide a unique theoretical argument that the Livestock Mandatory Price Reporting Act benefits producers by reducing beef packers' market power. Results from the third essay show the seller is indifferent between a posted price and auctioning an item when the seller and the buyers have similar noisy signals. However, when the seller has perfect information or buyers have less uncertainty than the seller, the seller prefers the posted-price market

Economics of Pre-Plant, Topdress, and Variable Rate Nitrogen Application in Winter Wheat

Past research about the efficiency of nitrogen application in winter wheat (Triticum aestivum L.) based on source and timing has produced inconsistent results. The majority of the literature used data from few locations over short time periods. This study used a unique data set of yields and nitrogen quantities from 2002-2009 at ten different locations in Oklahoma, USA. The objective of this research was to determine wheat yield response for granular pre-plant, uniform foliar topdress, and variable rate foliar topdress. Topdress liquid nitrogen had a 19% higher NUE than pre-plant urea, and was the most profitable source of nitrogen.linear stochastic plateau, nitrogen use efficiency, profitability, wheat, Crop Production/Industries,

La Segunda Guerra Mundial y la “crisis de producción” en los bosques mexicanos

Este artículo muestra que la Segunda Guerra Mundial representó un parteaguas para los bosques mexicanos. La guerra creó una inmensa demanda de productos forestales por parte de los Aliados y México respondió mediante la implementación de un sistema que denomino “el aprovechamiento de lacrisis”. El nuevo régimen productivo puso a un lado la política forestal existente, que favorecía el manejo cuidadoso de los recursos naturales, y la sustituyó por la tala comercial casi desmedida. La guerra también produjo escaseces sin precedentes de materias primas estratégicas, tales como el papel. En uncorto plazo, “el aprovechamiento de la crisis” produjo daños en el ecosistema forestal, pero su verdadero costo no se sintió sino después de la guerra, pues su lógica perduró hasta la década de 1980 en forma de códigos forestales que favorecieron la silvicultura comercial, así como las concesiones a largo plazo,otorgadas inicialmente a fábricas de papel y luego incluso a empresas madereras

Observation of Localized Multi-Spatial-Mode Quadrature Squeezing

Quantum states of light can improve imaging whenever the image quality and resolution are limited by the quantum noise of the illumination. In the case of a bright illumination, quantum enhancement is obtained for a light field composed of many squeezed transverse modes. A possible realization of such a multi-spatial-mode squeezed state is a field which contains a transverse plane in which the local electric field displays reduced quantum fluctuations at all locations, on any one quadrature. Using a traveling-wave amplifier, we have generated a multi-spatial-mode squeezed state and showed that it exhibits localized quadrature squeezing at any point of its transverse profile, in regions much smaller than its size. We observe 75 independently squeezed regions. The amplification relies on nondegenerate four-wave mixing in a hot vapor and produces a bichromatic squeezed state. The result confirms the potential of this technique for producing illumination suitable for practical quantum imaging

The Astronomy of Africa’s Health Systems Literature During the MDG Era: Where Are the Systems Clusters?

The volume of literature on health systems in sub-Saharan Africa has been expanding since the 2000 MDG era. Focus has remained generally on categorical health themes rather than systems concepts. Topics such as scaling-up, organizational development, data use for decision making, logistics, and financial planning remain underrepresented. And quite surprisingly, implementation science remains something of a “black hole.” But bibliometric evidence suggests there is a shift in focus that may soon address these gaps

Identifying Tennessee school-based agricultural education student growth and program accountability metrics

Over the years, accountability in education has transformed from the primary focus being the school as a whole to the individual teacher. The purpose of this study was to determine the metrics Tennessee school-based agricultural education teachers perceive as indicators of excellent total programs (classroom instruction, FFA, SAE), and a modified Delphi study was used to seek a consensus. The following nine metrics were retained: (a) pesticide certification, (b) program of activities, (c) number of students participating in CDEs, (d) chapter community service hours, (e) total number of FFA activities, (f) number of CDEs coached, (g) at least one proficiency at regional level, (h) one American degree every 3 years, and (i) percentage of students with SAE. Overall, the metrics agreed upon are narrow in focus and all but one is a record of activity and not direct measures of students’ knowledge or skills. As a result, the measures do not include student growth or value-added scores or authentic assessments of 21st century skills. Additional research is needed to further investigate the metrics that should be used to measure a school-based agricultural education program’s success in Tennessee and across the nation

Statistical methods for forecasting and estimating passenger willingness-to-pay in airline revenue management

Thesis (S.M.)--Massachusetts Institute of Technology, Sloan School of Management, Operations Research Center, 2010.Page 170 blank. Cataloged from PDF version of thesis.Includes bibliographical references (p. 167-169).The emergence of less restricted fare structures in the airline industry reduced the capability of airlines to segment demand through restrictions such as Saturday night minimum stay, advance purchase, non-refundability, and cancellation fees. As a result, new forecasting techniques such as Hybrid Forecasting and optimization methods such as Fare Adjustment were developed to account for passenger willingness-to- pay. This thesis explores statistical methods for estimating sell-up, or the likelihood of a passenger to purchase a higher fare class than they originally intended, based solely on historical booking data available in revenue management databases. Due to the inherent sparseness of sell-up data over the booking period, sell-up estimation is often difficult to perform on a per-market basis. On the other hand, estimating sell-up over an entire airline network creates estimates that are too broad and over-generalized. We apply the K-Means clustering algorithm to cluster markets with similar sell-up estimates in an attempt to address this problem, creating a middle ground between system-wide and per-market sell-up estimation. This thesis also formally introduces a new regression-based forecasting method known as Rational Choice. Rational Choice Forecasting creates passenger type categories based on potential willingness-to-pay levels and the lowest open fare class. Using this information, sell-up is accounted for within the passenger type categories, making Rational Choice Forecasting less complex than Hybrid Forecasting. This thesis uses the Passenger Origin-Destination Simulator to analyze the impact of these forecasting and sell-up methods in a controlled, competitive airline environment. The simulation results indicate that determining an appropriate level of market sell-up aggregation through clustering both increases revenue and generates sell-up estimates with a sufficient number of observations. In addition, the findings show that Hybrid Forecasting creates aggressive forecasts that result in more low fare class closures, leaving room for not only sell-up, but for recapture and spill-in passengers in higher fare classes. On the contrary, Rational Choice Forecasting, while simpler than Hybrid Forecasting with sell-up estimation, consistently generates lower revenues than Hybrid Forecasting (but still better than standard pick-up forecasting). To gain a better understanding of why different markets are grouped into different clusters, this thesis uses regression analysis to determine the relationship between a market's characteristics and its estimated sell-up rate. These results indicate that several market factors, in addition to the actual historical bookings, may predict to some degree passenger willingness-to-pay within a market. Consequently, this research illustrates the importance of passenger willingness-to-pay estimation and its relationship to forecasting in airline revenue management.by Christopher A. Boyer.S.M

Assessing model performance for counterfactual predictions

Counterfactual prediction methods are required when a model will be deployed in a setting where treatment policies differ from the setting where the model was developed, or when the prediction question is explicitly counterfactual. However, estimating and evaluating counterfactual prediction models is challenging because one does not observe the full set of potential outcomes for all individuals. Here, we discuss how to tailor a model to a counterfactual estimand, how to assess the model's performance, and how to perform model and tuning parameter selection. We also provide identifiability results for measures of performance for a potentially misspecified counterfactual prediction model based on training and test data from the same (factual) source population. Last, we illustrate the methods using simulation and apply them to the task of developing a statin-na\"{i}ve risk prediction model for cardiovascular disease