1. Introduction
During the outbreak of African Swine Fever (ASF) in South Korea in 2019, the media predicted that the pork supply would decrease and that pork prices would rise by the end of September of that year. At the end of October, after the ASF outbreak was controlled, however, pork prices collapsed due to a sharp fall in consumption [
1]. This situation is thought to have stemmed from the reduced will of consumers to purchase pork, as news about the ASF outbreak was reported and the information was delivered to consumers through various types of media, including SNS. When livestock epidemics such as ASF or Avian Influenza (AI) occur, they can have a negative effect on demand and cause volatile changes to livestock prices because the supply of livestock products will be reduced because of the pre-emptive slaughter of animals at risk and the fall in consumer demand [
2,
3]. Previous outbreaks such as Bovine Spongiform Encephalopathy and Foot and Mouth Disease demonstrated the effect on livestock products [
2,
4,
5,
6,
7]. News about livestock diseases was considered to be an advertisement against livestock consumption [
2,
5,
6].
Recently, the outbreak of infectious diseases like ASF, AI, Middle East respiratory syndrome (MERS), and COVID-19 have affected the whole world. Many data-based approaches and algorithms have been proposed to predict the spread of diseases and to use social media data for disaster management [
8,
9,
10,
11]. In this study, we wanted to test if there were threshold effects of infectious disease-related news on retail livestock prices and to determine the threshold values using a threshold autoregressive (TAR) model when there were outbreaks of major infectious diseases. We also aimed to determine if the response periods of livestock retail prices varied depending on the threshold effects after the price was initially affected. Finally, we compared the prediction accuracies of the TAR and autoregressive (AR) models of livestock retail prices to show the benefit of threshold models.
4. Discussion
In this study, we aimed to demonstrate that the threshold effects of the TAR model may be used for better livestock price predictions when epidemics such as ASF or AI occur since reduced supply and decreased consumption of livestock products can cause livestock prices to be volatile. TAR models have been influential in agricultural economics, including applications to pork price [
18], and there have been a few reports of the use of threshold models to explain the nonlinear structure of livestock prices caused by infectious diseases in pigs and broilers [
3,
19]. For example, the TAR model was employed to divide the nonlinear dynamics of pork prices in China into two regimes [
20,
21]. There are many variables that can affect the livestock products, such as the numbers of pigs bred and slaughtered, consumption of livestock products, feed prices, substitute prices, and weather. These variables may be included only exogenously in a time-series TAR model. Exogeneous variables in time series models may cause selection bias, which can reduce its prediction ability [
22]. Therefore, we focused on the threshold effects and levels that are determined within the model (endogenously) by omitting exogeneous variables. This study analyzed whether threshold effects existed in the retail prices of livestock products by considering news and SNS frequency which can influence and represent consumer sentiment.
Our findings suggest that when an infectious disease like ASF occurs for the first time, the threshold effects of the TAR model are observed and the price of pork shows a nonlinear relationship that can be divided into three regimes based on ASF-related news frequency, which indicates that the effect of disease-related news frequency on retail pork prices is significant. The impact response results showed that when ASF occurred for the first time on the Korean peninsula in 2019, the impact lasted for a long time in regime 1. However, after AI occurred multiple times, our findings also suggested that retail chicken prices had a linear relationship but no threshold effects, which indicated a reduced effect of AI news frequency on price. In the event of infectious disease outbreaks in livestock, the impacts on livestock prices and response periods were different depending on the regimes. Based on these findings, applying different policies to stabilize prices of livestock products depending the severity of the impact is necessary.
Recent reports have used unstructured data such as broadcast news, TV programs and social networks to predict pork demands or pork prices [
12,
23]. We proposed the use of SNS to promote pork consumption using ASF-related SNS frequency and its relationship to retail pork prices. Our findings suggest that when there was an increase in an ASF-related SNS frequency differences, the retail price of pork price rose by as much as 1.1666 Korean Won (KRW) in regime 1. Our findings indicate that more than 247 SNS posts are needed to encourage pork consumption and change the retail pork price by as much as one SD, which amounts to 288.2169 KRW. To the best of our knowledge, this study is the first to suggest the use of SNS to promote livestock consumption after it has collapsed because of an epidemic.
During the recent outbreak of ASF on the Korean peninsula, meat consumption and meat prices collapsed, an outcome not observed during the recent outbreak of AI. We wanted to apply the TAR model to estimate the threshold effects of infectious disease-related news on livestock retail prices after outbreaks of major infectious diseases. Therefore, this study specifically focused on whether threshold effects that make the livestock price nonlinear exist due to news and SNS frequency related to infectious diseases. However, this study has a few limitations. First, it did not consider the various factors that can affect livestock prices but looked only at disease-related news and SNS frequency. Second results were interpreted by speculation, and third, analysis of positive and negative news and SNS reporting was missing. For better livestock price prediction, it is necessary to study various factors that can affect prices and analyze the positive and negative content of news and SNS when infectious diseases occur.