The Shifting Patterns of Agricultural Production and Productivity Worldwide

In this book we assemble a range of evidence from a range of sources with a view to developing an improved understanding of recent trends in agricultural productivity around the world. The fundamental purpose is to better understand the nature of the long-term growth in the supply of food and its principal determinants. We pursue this purpose from two perspectives. One is from a general interest in the world food situation in the long run. The other is from an interest in the implications of U.S. and global productivity patterns for U.S. agriculture.https://lib.dr.iastate.edu/card_books/1001/thumbnail.jp

Letting Down the Team? Evidence of Social Effects of Team Incentives

This paper estimates social effects of incentivizing people in teams. In two field experiments featuring exogenous team formation and opportunities for repeated social interactions, we find large team effects that operate through social channels. The team compensation system induced agents to choose effort as if they valued a marginal dollar of compensation for their teammate from two-thirds as much (in one study) to twice as much as they valued a dollar of their own compensation (in the other study). We conclude that social effects of monetary team incentives exist and can induce effort at lower cost than through direct individual payment.

State Variation in the Determinants of Motor Vehicle Fatalities

Research on motor vehicle safety has involved virtually all modes of transportation. Most of these have been national in scope with relatively few studies focused on the determinants of motor vehicle fatalities at the state level. This paper investigates the determinants of motor vehicle fatalities across the states of California, Illinois, Louisiana, Pennsylvania, and Texas, which collectively account for 27% of U.S. motor vehicle fatalities in 2006. An important finding is that fatalities vary significantly by state even after controlling for commonly cited fatality determinants

Specifying and Estimating a Regional Agricultural Railroad Demand Model

In recent years there have been few railroad demand studies. Also, no study has investigated the possibility of regional differences in railroad demand. The objective of the paper is to estimate railroad demand functions for wheat, corn, sorghum, and soybeans for the United States as well as the east and west regions. A two-region spatial equilibrium model is employed to specify the empirical model in which railroad tons originated is the dependent variable. The explanatory variables include railroad price per ton, crop production, and barge price per ton. The theoretically expected sign is negative for rail price. Alternatively, the expected sign is positive for crop production and barge rate. Results include estimates of railroad own-price elasticities and cross price elasticities relative to barge transport. The estimates also reveal regional differences in railroad grain demand

Reduced-Class Distinctions: Effort, Ability, and the Education Production Function

Do smaller classes boost achievement mainly by helping teachers impart specific academic skills to students with low academic achievement? Or do they do so primarily by helping teachers engage poorly behaving students? The analysis uses the grade 3 to 4 transition in San Diego Unified School District as a source of exogenous variation in class size (given a California law funding small classes until grade 3). Grade 1 report cards allow separate identification of low-effort and low-achieving students. Results indicate that elicitation of effort or engagement, rather than the teaching of specific skills, may be the dominant channel by which small classes influence disadvantaged students.

Placing bounds on extreme temperature response of maize

Plant water availability is a key factor that determines maize yield response to excess heat. Lack of available data has limited researchers\u27 ability to estimate this relationship at regional and global scales. Using a new soil moisture data set developed by running a crop growth simulator over historical data we demonstrate how current estimates of maize yield sensitivity to high temperature are misleading. We develop an empirical model relating observed yields to climate variables and soil moisture in a high maize production region in the United States to develop bounds on yield sensitivity to high temperatures. For the portion of the region with a relatively long growing season, yield reduction per °C is 10% for high water availability and 32.5% for low water availability. Where the growing season is shorter, yield reduction per °C is 6% for high water availability and 27% for low water availability. These results indicate the importance of using both water availability and temperature to model crop yield response to explain future climate change on crop yields

Late-1990s Climate Shift Impact on Corn Yield in Iowa

The next advance in climate science will come out of experiments in forecasting shifts in climate regimes—an extended period of time in which weather conditions have consistent range, such as the Dust Bowl years or the Little Ice Age. A climate regime shift results in a new range of weather conditions for an extended period, so being able to predict a regime shift allows planners to anticipate an emerging weather risk profile that would be expected to persist for 20–30 years. One way a regime change occurs is when slowly varying ocean surface temperatures change from warm to cold. In the Corn Belt, summer rainfall is influenced over 20–30 year periods by two recurring ocean surface temperature patterns: the Pacific Decadal Oscillation (PDO) (Hu and Feng 2001) and the Atlantic Multidecadal Oscillation (AMO) (Hu et al. 2011). Together they have four phases of warm and cold conditions that result in four different spatial patterns for drought risk across the United States (McCabe et al. 2004). While climate scientists will focus on decadal forecast capability for broad temperature and rainfall patterns, the more immediate question for agriculture is, how have climate regime shifts affected yield

Semi-Markov adjunction to the Computer-Aided Markov Evaluator (CAME)

The rule-based Computer-Aided Markov Evaluator (CAME) program was expanded in its ability to incorporate the effect of fault-handling processes into the construction of a reliability model. The fault-handling processes are modeled as semi-Markov events and CAME constructs and appropriate semi-Markov model. To solve the model, the program outputs it in a form which can be directly solved with the Semi-Markov Unreliability Range Evaluator (SURE) program. As a means of evaluating the alterations made to the CAME program, the program is used to model the reliability of portions of the Integrated Airframe/Propulsion Control System Architecture (IAPSA 2) reference configuration. The reliability predictions are compared with a previous analysis. The results bear out the feasibility of utilizing CAME to generate appropriate semi-Markov models to model fault-handling processes

Approaches to healthcare personnel exemption requests from coronavirus disease 2019 (COVID-19) vaccination: Results of a national survey

OBJECTIVE: Although a growing number of healthcare facilities are implementing healthcare personnel (HCP) coronavirus disease 2019 (COVID-19) vaccination requirements, vaccine exemption request management as a part of such programs is not well described. DESIGN: Cross-sectional survey. PARTICIPANTS: Infectious disease (ID) physician members of the Emerging Infections Network with infection prevention or hospital epidemiology responsibilities. METHODS: Eligible persons were sent a web-based survey focused on hospital plans and practices around exemption allowances from HCP COVID-19 vaccine requirements. RESULTS: Of the 695 ID physicians surveyed, 263 (38%) responded. Overall, 160 respondent institutions (92%) allowed medical exemptions, whereas 132 (76%) allowed religious exemptions. In contrast, only 14% (n = 24) allowed deeply held personal belief exemptions. The types of medical exemptions allowed varied considerably across facilities, with allergic reactions to the vaccine or its components accepted by 145 facilities (84%). For selected scenarios commonly used as the basis for religious and deeply held personal belief exemption requests, 144 institutions (83%) would not approve exemptions focused on concerns regarding right of consent or violations of freedom of personal choice, and 140 institutions (81%) would not approve exemptions focused on introducing foreign substances into one\u27s body or the sanctity of the body. Most respondents noted plans for additional infection prevention interventions for HCP who received an exemption for COVID-19 vaccination. CONCLUSIONS: Although many respondent institutions allowed exemptions from HCP COVID-19 vaccination requirements, the types of exemptions allowed and how the exemption programs were structured varied widely