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  1. Article: On the Treatment of Heteroscedasticity in Crop Yield Data

    Ker, Alan P / Tolhurst, Tor N

    American journal of agricultural economics. 2019 July, v. 101, no. 4

    2019  

    Abstract: In empirical applications with crop yield data, conditioning for heteroscedasticity is both important and challenging. It is important because the scale of the distribution can markedly influence the results, and challenging because statistical tests for ...

    Abstract In empirical applications with crop yield data, conditioning for heteroscedasticity is both important and challenging. It is important because the scale of the distribution can markedly influence the results, and challenging because statistical tests for the common heteroscedasticity assumptions (constant or proportional variance) often lead to ambiguous conclusions. Alternatively, Harri et al. (2011) proposed a methodology that estimates the degree of heteroscedasticity, removing the need to make a specific assumption. Such approaches assume that volatility changes are symmetric (identical) across tails of the yield distribution. We propose a generalization to the Harri et al. (2011) methodology, which allows asymmetry between the tails, akin to the generalization of GARCH to AGARCH. Using U.S. county level yield data from 1951–2017, we find evidence of asymmetry in corn and soybean, but not wheat. Moreover, the asymmetry takes a particular form—increasing volatility in the lower tail. To investigate economic significance, we consider the effect of imposing symmetric heteroscedasticity in rating crop insurance contracts, as currently done by the USDA's Risk Management Agency in rating their Area Risk Protection products. We find that relaxing the symmetry assumption leads to economically and statistically significant rents. Our results suggest that the Risk Management Agency and others should consider the possibly asymmetric nature of heteroscedasticity in crop yield data.
    Keywords USDA ; corn ; crop insurance ; crop yield ; heteroskedasticity ; risk ; risk management ; soybeans ; variance ; wheat ; United States
    Language English
    Dates of publication 2019-07
    Size p. 1247-1261.
    Publishing place Oxford University Press
    Document type Article
    Note JOURNAL ARTICLE
    ZDB-ID 218188-5
    ISSN 0002-9092
    ISSN 0002-9092
    DOI 10.1093/ajae/aaz004
    Database NAL-Catalogue (AGRICOLA)

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  2. Article: Bayesian estimation of possibly similar yield densities

    Ker, Alan P / Liu, Yong / Tolhurst, Tor N

    American journal of agricultural economics Vol. 98, No. 2 , p. 360-382

    implications for rating crop insurance contracts

    2016  Volume 98, Issue 2, Page(s) 360–382

    Author's details Alan P. Ker, Tor N. Tolhurst and Yong Liu
    Keywords Rating crop insurance contracts ; Bayesian model averaging ; multiple density estimation ; spatial correlation ; small sample estimation
    Language English
    Publisher Oxford University Press
    Publishing place Cary, NC
    Document type Article
    ZDB-ID 218188-5
    ISSN 0002-9092
    ISSN 0002-9092
    Database ECONomics Information System

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  3. Article: Bayesian Estimation of Possibly Similar Yield Densities: Implications for Rating Crop Insurance Contracts

    Ker, Alan P / Tolhurst, Tor N / Liu, Yong

    American journal of agricultural economics. 2016 Mar., v. 98, no. 2

    2016  

    Abstract: The Agricultural Act of 2014 solidified insurance as the cornerstone of U.S. agricultural policy. The Congressional Budget Office (2014) estimates that this act will increase spending on agricultural insurance programs by $5.7 billion to a total of $89.8 ...

    Abstract The Agricultural Act of 2014 solidified insurance as the cornerstone of U.S. agricultural policy. The Congressional Budget Office (2014) estimates that this act will increase spending on agricultural insurance programs by $5.7 billion to a total of $89.8 billion over the next decade. In light of the sizable resources directed toward these programs, accurate rating of insurance contracts is of the utmost importance to producers, private insurance companies, and the federal government. Unlike most forms of insurance, agricultural insurance is plagued by a paucity of spatially correlated data. A novel interpretation of Bayesian Model Averaging is used to estimate a set of possibly similar densities that offers greater efficiency if the set of densities are similar while seemingly not losing any if the set of densities are dissimilar. Simulations indicate that finite sample performance—in particular small sample performance—is quite promising. The proposed approach does not require knowledge of the form or extent of any possible similarities, is relatively easy to implement, admits correlated data, and can be used with either parametric or nonparametric estimators. We use the proposed approach to estimate U.S. crop insurance premium rates for area-type programs and develop a test to evaluate its efficacy. An out-of-sample game between private insurance companies and the federal government highlights the policy implications for a variety of crop-state combinations. Consistent with the simulation results, the performance of the proposed approach with respect to rating area-type insurance—in particular small sample performance—remains quite promising.
    Keywords Bayesian theory ; Farm Bill ; business enterprises ; crop insurance ; federal government ; United States
    Language English
    Dates of publication 2016-03
    Size p. 360-382.
    Publishing place Oxford University Press
    Document type Article
    ZDB-ID 2026345-4
    ISSN 1467-8276 ; 0002-9092
    ISSN (online) 1467-8276
    ISSN 0002-9092
    DOI 10.1093/ajae/aav065
    Database NAL-Catalogue (AGRICOLA)

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  4. Article: Balancing Bees and Pest Management: Projected Costs of Proposed Bee-Protective Neonicotinoid Regulation in California

    Mace, Kevi / Rudder, Jessica / Goodhue, Rachael / Tolhurst, Tor / Tregeagle, Daniel / Wei, Hanlin / Grafton-Cardwell, Beth / Grettenberger, Ian / Wilson, Houston / Van Steenwyk, Robert / Zalom, Frank / Steggall, John

    Journal of economic entomology. 2021 Nov. 26, v. 115, no. 1

    2021  

    Abstract: Neonicotinoid insecticides are widely used in agriculture, including in many California specialty crops. With mounting evidence that these insecticides are harmful to bees, state and national governments have increasingly regulated their use. The ... ...

    Abstract Neonicotinoid insecticides are widely used in agriculture, including in many California specialty crops. With mounting evidence that these insecticides are harmful to bees, state and national governments have increasingly regulated their use. The European Union, Canada, and United States have imposed use restrictions on several neonicotinoids, such as on the timing of applications. In 2020, California proposed a draft regulation to mitigate harm to managed pollinators from four nitroguanidine-substituted neonicotinoids (NGNs): clothianidin, dinotefuran, imidacloprid, and thiamethoxam. We use data on California pesticide use from 2015 to 2017 to analyze the economic and pest management implications of the 2020 draft proposed regulation for seven crops: almond, cherry, citrus, cotton, grape, strawberry, and tomato. From 2015 to 2017, these crops accounted for approximately 85% of total hectares treated with NGNs and 87% of NGN use by kilograms of active ingredient applied in treatments that would have been affected by the proposed regulation. These insecticides often primarily target Hemipteran insect pests. In most cases there are alternatives; however, these are often more expensive per hectare and do not have the same residual effectiveness as the NGNs, which are systemic insecticides. Overall, we estimate that pest management costs for these crops would have increased an estimated $13.6 million in 2015, $12.8 million in 2016, and $11.1 million in 2017 if the 2020 draft proposed regulation had been in effect, representing a 61% to 72% increase in the cost of managing the target pests. Graphical Abstract
    Keywords Citrus ; European Union ; Hemiptera ; active ingredients ; almonds ; cherries ; clothianidin ; cotton ; dinotefuran ; entomology ; grapes ; imidacloprid ; strawberries ; thiamethoxam ; tomatoes ; California ; Canada
    Language English
    Dates of publication 2021-1126
    Size p. 10-25.
    Publishing place Entomological Society of America
    Document type Article
    ZDB-ID 3031-4
    ISSN 0022-0493
    ISSN 0022-0493
    DOI 10.1093/jee/toab231
    Database NAL-Catalogue (AGRICOLA)

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  5. Article: On technological change in crop yields

    Tolhurst, Tor N / Ker, Alan P

    American journal of agricultural economics Vol. 97, No. 1 , p. 137-158

    2015  Volume 97, Issue 1, Page(s) 137–158

    Author's details Tor N. Tolhurst and Alan P. Ker
    Keywords Climate ; crop insurance ; mixture models ; technological change ; yields
    Language English
    Size graph. Darst.
    Publisher Oxford University Press$h1968-
    Publishing place Cary, NC
    Document type Article
    ZDB-ID 218188-5
    ISSN 0002-9092
    ISSN 0002-9092
    Database ECONomics Information System

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  6. Article: On Technological Change in Crop Yields

    Tolhurst, Tor N / Ker, Alan P

    American journal of agricultural economics. 2015 Jan., v. 97, no. 1

    2015  

    Abstract: Technological changes in agriculture tend to alter the mass associated with segments or components of the yield distribution as opposed to simply shifting the entire distribution upwards. We propose modeling crop yields using mixtures with embedded trend ...

    Abstract Technological changes in agriculture tend to alter the mass associated with segments or components of the yield distribution as opposed to simply shifting the entire distribution upwards. We propose modeling crop yields using mixtures with embedded trend functions to account for potentially different rates of technological change in different components of the yield distribution. By doing so we can test some interesting and previously untested hypotheses about the data generating process of yields. For example: (1) is the rate of technological change equivalent across components, and (2) are the probabilities of components constant over time? Our results—technological change is not equivalent across components and probabilities tend not to have changed significantly over time—have implications for modeling yields. We find estimated conditional yield densities are quite different when unique trend functions are embedded inside the mixture components versus estimating the same mixture with detrended data. Also, we prove different rates of technological change in different components lead to nonconstant variance with respect to time (i.e., heteroscedasticity). We present two applications of the proposed yield model. The first application considers climate determinants of component membership, where our results are consistent with the literature for climate determinants of yields. The second application compares the proposed yield model to USDA's current rating methodology for area‐yield crop insurance contracts and finds the proposed model may lead to more accurate rates.
    Keywords USDA ; agricultural economics ; climate ; crop yield ; heteroskedasticity ; models ; technological change ; variance
    Language English
    Dates of publication 2015-01
    Size p. 137-158.
    Publishing place Oxford University Press
    Document type Article
    Note JOURNAL ARTICLE
    ZDB-ID 218188-5
    ISSN 0002-9092
    ISSN 0002-9092
    DOI 10.1093/ajae/aau082
    Database NAL-Catalogue (AGRICOLA)

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  7. Article: Canadian business risk management: private firms, crown corporations, and public institutions

    Ker, Alan P / Barnett, Barry J / Jacques, David / Tolhurst, Tor

    Canadian journal of agricultural economics : CJAE Vol. 65, No. 4 , p. 591-612

    2017  Volume 65, Issue 4, Page(s) 591–612

    Author's details Alan P. Ker, Barry Barnett, David Jacques and Tor Tolhurst
    Keywords Risikomanagement ; Agrarpolitik ; Agrarsubvention ; Agrarversicherung ; Bewertung ; Kanada
    Language English
    Publisher Soc
    Publishing place Ottawa [u.a.]
    Document type Article
    ZDB-ID 417256-5
    ISSN 0008-3976
    ISSN 0008-3976
    Database ECONomics Information System

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  8. Conference proceedings ; Online: On Technological Change in Crop Yields

    Tolhurst, Tor / Ker, Alan P.

    2013  

    Abstract: Technological change in plant research rarely shifts the entire yield distribution upwards as assumed in the agricultural economics literature. Rather, technologies have been targeted at a specific subpopulation of the yield distribution--for example, ... ...

    Abstract Technological change in plant research rarely shifts the entire yield distribution upwards as assumed in the agricultural economics literature. Rather, technologies have been targeted at a specific subpopulation of the yield distribution--for example, drought resistant seeds or so-called racehorse seeds--therefore, it is unlikely technological advancements are equal across subpopulations. In this manuscript we introduce a mixture model of crop yields with an embedded trend function in the component means, which allows different rates of technological change in each mixture or subpopulation. By doing so, we can test some interesting hypotheses that have been previously untestable. While previous literature assumes an equivalent rate of technological change across subpopulations we reject the null in 84.0%, 82.3%, and 64.0% of the counties for corn, soybean, and wheat respectively. Conversely, with respect to stable subpopulations through time (i.e. climate change) we reject in only 12.0%, 5.4%, and 4.6% of the counties for corn, soybean, and wheat respectively. These results have implications for modelling yields, directing funds regarding plant science research, and explaining the prevalence of heteroscedasticity in yield data.
    Keywords Crop Production/Industries
    Language English
    Publishing country us
    Document type Conference proceedings ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  9. Article ; Online: Balancing Bees and Pest Management: Projected Costs of Proposed Bee-Protective Neonicotinoid Regulation in California.

    Mace, Kevi / Rudder, Jessica / Goodhue, Rachael / Tolhurst, Tor / Tregeagle, Daniel / Wei, Hanlin / Grafton-Cardwell, Beth / Grettenberger, Ian / Wilson, Houston / Van Steenwyk, Robert / Zalom, Frank / Steggall, John

    Journal of economic entomology

    2021  Volume 115, Issue 1, Page(s) 10–25

    Abstract: Neonicotinoid insecticides are widely used in agriculture, including in many California specialty crops. With mounting evidence that these insecticides are harmful to bees, state and national governments have increasingly regulated their use. The ... ...

    Abstract Neonicotinoid insecticides are widely used in agriculture, including in many California specialty crops. With mounting evidence that these insecticides are harmful to bees, state and national governments have increasingly regulated their use. The European Union, Canada, and United States have imposed use restrictions on several neonicotinoids, such as on the timing of applications. In 2020, California proposed a draft regulation to mitigate harm to managed pollinators from four nitroguanidine-substituted neonicotinoids (NGNs): clothianidin, dinotefuran, imidacloprid, and thiamethoxam. We use data on California pesticide use from 2015 to 2017 to analyze the economic and pest management implications of the 2020 draft proposed regulation for seven crops: almond, cherry, citrus, cotton, grape, strawberry, and tomato. From 2015 to 2017, these crops accounted for approximately 85% of total hectares treated with NGNs and 87% of NGN use by kilograms of active ingredient applied in treatments that would have been affected by the proposed regulation. These insecticides often primarily target Hemipteran insect pests. In most cases there are alternatives; however, these are often more expensive per hectare and do not have the same residual effectiveness as the NGNs, which are systemic insecticides. Overall, we estimate that pest management costs for these crops would have increased an estimated $13.6 million in 2015, $12.8 million in 2016, and $11.1 million in 2017 if the 2020 draft proposed regulation had been in effect, representing a 61% to 72% increase in the cost of managing the target pests.
    MeSH term(s) Animals ; Bees ; Crops, Agricultural ; Insecta ; Insecticides/analysis ; Neonicotinoids ; Nitro Compounds ; Thiamethoxam
    Chemical Substances Insecticides ; Neonicotinoids ; Nitro Compounds ; Thiamethoxam (747IC8B487)
    Language English
    Publishing date 2021-12-10
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 3031-4
    ISSN 1938-291X ; 0022-0493
    ISSN (online) 1938-291X
    ISSN 0022-0493
    DOI 10.1093/jee/toab231
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    Zs.B 1118: Show issues Location:
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    bis Jg. 2021: Bestellungen von Artikeln über das Online-Bestellformular
    ab Jg. 2022: Lesesaal (EG)

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  10. Article: The economic impact of a foot-and-mouth disease outbreak for Ontario's beef sector

    Cairns, Alexander / Duff, Stephen / Jacques, David / Ker, Alan P / Poon, Kenneth / Tolhurst, Tor / Yang, Lin

    Canadian journal of agricultural economics : CJAE Vol. 65, No. 1 , p. 159-183

    2017  Volume 65, Issue 1, Page(s) 159–183

    Author's details Alexander Cairns, Tor Tolhurst, Kenneth Poon, Alan P. Ker, Stephen Duff, David Jacques and Lin Yang
    Keywords Tierkrankheit ; Rindermarkt ; Fleischmarkt ; Tierschutz ; Wohlfahrtsanalyse ; Partielles Gleichgewicht ; Ontario (Provinz) ; Kanada
    Language English
    Publisher Soc
    Publishing place Ottawa [u.a.]
    Document type Article
    ZDB-ID 417256-5
    ISSN 0008-3976
    ISSN 0008-3976
    Database ECONomics Information System

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