Estimation of peach supply response in Colombia using a Vector Error Correction Model / Estimación de la respuesta de la oferta de durazno en Colombia mediante el modelo de vector de corrección de errores / Estimativa da resposta de fornecimento de pêssego na Colômbia usando um Modelo de Correcção de Erros Vectoriais

ABSTRACT An empirical study of peach supply response to own-price and yield in Colombia using time series data from 2000 to 2018 was undertaken. A quantitative, correlational and non-experimental research design was selected and the Johansen's co-integration as well as the vector error correction framework were employed. The Augmented Dickey-Fuller test showed that the time series were integrated of order one and the Johansen's co-integration confirmed the existence of a long-term relationship between the variables. Moreover; the short and long run coefficients for own-price and yield were statistically significant and presented the expected signs, however estimated own-price elasticity was below unit suggesting it is not an important factor in peach supply response. Furthermore, the vector error correction coefficient (-0.32) was negative and in line with theory which showed that in the long-run, the model converges towards equilibrium, however at a relatively slow pace. Therefore, it can be concluded that, overall, the proposed model contributes to the understanding of the dynamics in peach output supply

RESUMEN Se realizó un estudio empírico sobre la respuesta a la oferta de durazno con relación a su precio y rendimiento agr'cola en Colombia, utilizando datos de series de tiempo para el per'odo comprendido entre 2000 y 2018. Se seleccionó un diseño de investigación cuantitativo, correlacional y no experimental y se empleó la cointegración de Johansen y el modelo de vector de corrección de errores. Los resultados de la a prueba de Aumentada de Dickey-Fuller demostraron que las series temporales estaban integradas en el orden uno y la cointegración de Johansen confirmó la existencia de una relación a largo plazo entre las variables. Además, los coeficientes del precio y rendimiento a largo y corto plazo fueron estadísticamente significativos y presentaron los signos esperados. Sin embargo, la elasticidad precio estimada fue inferior a la unidad, lo cual sugiere que no es un factor importante en la respuesta de la oferta de durazno. Asimismo, el coeficiente de corrección de error del vector (-0.32) fue negativo y en línea con la teoría, denostando que, a largo plazo, el modelo converge hacia al equilibrio, pero a una velocidad relativamente lenta. Por lo tanto, se puede concluir que, en general, el modelo propuesto, contribuye a la comprensión de la dinámica de la respuesta de la oferta de durazno.

RESUMO Realizou-se um estudo empírico da resposta da oferta de pêssego em função do seu preço e rendimento agrícola na Colômbia, usando dados de séries temporais para o período entre 2000 a 2018. O estudo usou um desenho de pesquisa quantitativa, correlacional e não experimental assim como a cointegração de Johansen e o modelo Vetorial de Correção de Erro. Os resultados do teste Aumentado de Dickey-Fuller demonstraram que as séries são integradas de ordem um e a cointegração de Johansen confirmou a existência de uma relação de longo prazo entre as variáveis. Além disso, os coeficientes do curto e longo prazo para preço e rendimento foram estatisticamente significantes e apresentaram os sinais esperados; no entanto, a elasticidade estimada do preço foi menor que a unidade, sugerindo que não é um fator importante na resposta da oferta de pêssego. Além disso, o coeficiente de correção de erros vetoriais (-0,32) foi negativo e alinhado à teoria, que mostrou que, a longo prazo, o modelo converge para o equilíbrio, porém a um ritmo relativamente lento. Portanto, pode-se concluir que, de maneira geral, o modelo proposto contribui para entender a dinâmica da oferta de produção de pêssego.

Study on Chinese medicinal materials origin market integration--Taking Lonicerae Japonicae Flos, Lycii Fructus, Isatidis Radix and Pseudostellariae Radix for examples / 中草药

Trading volume in Chinese medicinal materials market has gradually declined, and origin market trade has become a trend. Studying the degree of market integration is helpful to understand the operation of origin market of Chinese medicinal materials, which is of great significance for rational planning of the production of Chinese medicinal materials and improving market efficiency. In this study, four varieties (Lonicerae Japonicae Flos, Lycii Fructus, Isatidis Radix and Pseudostellariae Radix) were selected to study the market integration degree of Chinese medicinal materials. Based on the price index data from 2013 to 2019, this paper makes an empirical analysis by using co-integration test, error correction model and Granger causality test. The results showed that the long-term integration of Chinese medicinal materials market was relatively high, but the short-term integration was far lower than the long-term integration. Finally, the author puts forward four policy suggestions: improving the price information platform conduction of Chinese medicinal materials, building high-quality brand of Chinese medicinal materials in non-authentic producing areas, speeding up the establishment quality traceability system and building modern logistics system of Chinese medicinal materials.

Review on correction methods related to the pleiotropic effect in Mendelian randomization / 中华流行病学杂志

Mendelian randomization is an approach using the genetic variants as instrumental variable to estimate and assess the casual relationship between exposure of interest and outcomes. As a valid instrument, genetic variants have to meet the assumptions of strong correlation with exposure but without pleiotropic effect with the outcomes. However, pleiotropy of the variants is usually inevitable, owing to the existence of complex biological effects. Thus, correction methods related to pleiotropic bias are introduced in this paper regarding the selection of instrumental variables, testing of invalid instrumental variables, construction of pleiotropic effect correction models and sensitivity analysis of the robust results. For practical application, investigators should take consideration on the following areas including the types of data, sample size and other relative aspects, thereby selecting the suitable method for the inference of consistent and robust casual estimation.

Dynamic econometrical analysis on effects of health resources inputs on residents health in Beijing / 中华医院管理杂志

Objective To learn the present status of health resources in Beijing and analyze the scale and direction of the impacts of health resources inputs on health outputs. Methods To avoid spurious regression of time sequence, macro statistics of health indicators were collected from four districts, with co-integration test and error correction model used, to analyze the impacts of health resources inputs and health demands on residents′ health outputs. Results The indicators of the number of hospital beds per thousand people, government health expenditure and disposable income of residents had positive influence on health outputs, while the ratio of doctor and nurse, and the dependency ratio of population were the two negative impacts on health. But there was no significant difference between these two negative effect indicators. Conclusions Health improvement can be promoted by increased medical and health resources, but better balance of health resources allocation is imperative among regions. More nursing personnel should be trained in order to improve the efficiency of human resource for health. The government health expenditure should be improved so as to build continuous medical service system.