Elizabeth Nolan

The Contribution of Genetic Modification to Changes in Corn Yield in the United States

We use a large, rich dataset compiled from results of university extension trials to estimate the contribution of genetic modification (GM) to changes in corn yield in the United States from timeA to timeB. Through repeated experimental trials, we obtain consistent estimates of the effect of these traits by using both the Hausman-Taylor estimator and a comparison of fixed effects estimates analogous to the agronomic practice of comparing near-isolines. Our results suggest that GM traits had a positive impact on yield, but that gains associated with combining several GM traits in one hybrid are not necessarily additive. Copyright 2012, Oxford University Press.

An Analysis of Selectivity in the Productivity Evaluation of Biotechnology: An Application to Corn

We investigate selectivity bias in the evaluation of biotech hybrid productivity. The analysis is applied to experimental data on Wisconsin corn yields from 1990 to 2010. Relying on a Heckman-like factor that accounts for selectivity, we find evidence of selection bias, indicating that some of the observed yield advantage associated with GM hybrids can be attributed to their conventional genes. We document how the rising market concentration of biotech firms has contributed to increasing selectivity bias in corn yield. The impact, however, is offset by the negative effect of the rising adoption rate of GM corn on selectivity bias. Copyright 2013, Oxford University Press.

Valuing Quality Attributes of Australian Merino Wool

We measure the relationship between clean prices of individual lots of wool sold at auction and a range of characteristics of the raw wool. Based on the data for 111,440 fleece lots sold in the 2008–2009 auction season, five hedonic models are estimated to determine the premiums and discounts associated with each wool characteristic in five micron categories. Several wool characteristics exhibited significant nonlinear relationships, and therefore, joint density functions were assessed where appropriate. The results indicate that fibre diameter has the greatest influence on price in all markets. Brand contamination, higher levels of unscourable colour and vegetable matter contamination were found to negatively influence price.

Predicting Performance in Undergraduate Agricultural Economics

Entry to the Bachelor of Agricultural Economics (BAgrEc) program at the University of Sydney is consistently less competitive than that for the Bachelor of Economics (BEc) and Bachelor of Commerce (BComm) programs. Given that students in the BAgrEc program undertake units in common with students in the BEc and BComm programs, it is of interest to examine the importance of school performance and first year university in the determination of success at university. This paper takes information for nine cohorts of BAgrEc students and tests their performance in first-year core subjects against the university entrance ranking, school English and mathematics marks, gender, and type of school. The paper then uses the same information to predict which student characteristics at entry level are likely to lead to students completing the degree program. The implications of the analysis are explored.