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Autor	Katarzyna Czech, Michał Wielechowski
Tytuł	ARE AGRICULTURAL COMMODITY PRICES AFFECTED BY COVID-19? A STRUCTURAL BREAK IDENTIFICATION
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Słowa kluczowe	agricultural commodities, stock market, COVID-19, structural breaks
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Abstrakt	The paper aims to identify the COVID-19-driven structural break in agricultural commodity prices time series. We assume the official outbreak of the COVID-19 pandemic, i.e., 11 March 2020, as the breaking point. We use data on the S&P GSCI Agriculture and Livestock Index and the S&P 500 from Refinitiv Datastream. The structural break is identified based on the Chow test. We prove the existence of structural break in both the S&P 500 and the S&P GSCI Agriculture and Livestock Index triggered by the official outbreak of the COVID-19 pandemic. Moreover, to assess the causality between the analysed series, we apply the Granger causality test. We reveal a unidirectional causal relationship from the stock market to the agricultural commodity market.
Abstract
Cytowanie	Czech K., Wielechowski M.
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Pełny tekst	ESARE_2020_n4_s37.pdf

Autor	Katarzyna Czech
Tytuł	Structural Changes in Wheat Market
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Słowa kluczowe
Key words	agricultural commodity, wheat market, structural breaks, Bai-Perron test
Abstrakt
Abstract	Time series analysis is based on the assumption of stationarity. Stationarity implies the parameters are constant over time. Structural break occurs when at least one of the parameters changes at some date. Structural breaks can lead to huge forecasting errors and unreliability of the model. Modelling structure breaks is very popular in the literature of macroeconomics and finance. However, there are still too few publications about structural breaks in agricultural market. The goal of research is to identify structural breaks in wheat prices time series. A few structural break tests are applied. It has been shown that there is at least one significant structural break in the analysed time series. Both Quandt-Andrews and Bai-Perron tests show that there is a significant breakpoint in 12.09.2007. The estimated break date is associated with the beginning of global financial crisis. It may imply that wheat prices have become more prone to changes in global financial market.
Cytowanie	Czech K. (2016) Structural Changes in Wheat Market.Zeszyty Naukowe SGGW w Warszawie - Problemy Rolnictwa Światowego, t. 16(31), z. 4: 92-98
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Pełny tekst	PRS_2016_T16(31)_n4_s92.pdf