Introduction
Coronavirus (COVID-19) outbreak has wreaked havoc globally. Overburdened hospitals, staggering death tolls, and transportation disruptions, coupled with the initial limited understanding of COVID-19, have plunged people into deep fear. Urgency encourages people to seek, share, and post information on social media. However, this triggered an infodemic (information pandemic), in which there is too much information, including false or misleading information, on social media. It caused confusion and spillover effects. For example, March 2020 witnessed one of the most dramatic stock market crashes in history, with the Dow Jones Industrial Average (DJIA) plummeting by 6,400 points, or approximately 26%, in just four trading days (
Mazur et al., 2021). Strong negative information was projected to collapse the U.S. stock market by 2020 (
Moalla & Dammak, 2023;
Ozili & Arun, 2023). Because infodemics can affect more than just the financial world, the World Health Organization (WHO) calls for research on the COVID-19 infodemic and its consequences across various fields (
WHO 2023).
Pandemics (similar to the Spanish Flu of 1918 and the Black Death of the 14th century), are very rare. Therefore, knowledge about how information flows during pandemics and how it affects society is limited (
Wagner, 2020). COVID-19 infodemic, as an information crisis, occurs primarily on social media. When social media coverage of an issue about COVID-19 increases, the salience of COVID-19 also increases (
Scheufele, 2000). This is true not only for the general public but also for financial experts and investment markets. Their assessments of the current economic situation and expectations are largely determined by their knowledge derived from many sources, including social media. These decisions lead to changes in investment decisions and affect stock market volatility (
Nepp et al., 2022). In other words, news content drives market sentiment (
Shiller, 2015) and trading behavior.
Unfortunately, information (news) on social media is mostly negative (i.e., fearful) (
Lwin et al., 2020;
Naseem et al., 2021). This negative information affects investor sentiment (
W. Yang et al., 2017), leading to increased anxiety (
Garfin et al., 2020), fear, and panic (
Atri et al., 2021). Ultimately, negative information is transferred to the financial markets through panic-stricken investors (
Nepp et al., 2022). Furthermore, more negative sentiment generates greater attention, creating a vicious cycle of information crisis.
Research on the relationship between information (news) and finances shows that COVID-19 information (news), sentiments, panic, and media hype affect the stock markets (
Deng et al., 2023;
Huynh et al., 2021;
X. Li, 2021;
Szczygielski et al., 2023;
Valle-Cruz et al., 2022;
Zargar & Kumar, 2023). However, most studies have focused on the financial perspective rather than the information (news) diffusion process. Thus, when the next crisis occurs, we will not know how to prevent stock markets from collapsing by interrupting the information (news) diffusion process. Thus, a new approach based on communication science is required to understand the information (news) diffusion process that affects trading behavior.
Agenda-setting (
M. E. McCombs & Shaw, 1972) and the diffusion of innovations (
Rogers, 2003) focus on the role of influential opinion leaders or early adopters in shaping public opinion. However, owing to the abundance and diversity of opinion leaders, conflicting and unprofessional information from the media and political and public health opinion leaders often compete for viewers’ attention. Regrettably, few studies pay attention to opinion leaders’ agendas. Even if studies focus on agendas of opinion leaders (
A. Chen et al., 2022;
Gollust et al., 2020;
Mourad et al., 2020), they do not differentiate between the different types. Importantly, different types of agenda can shape different models of financial communication in times of crisis.
Clearly, a theoretical gap in financial communication models exists regarding how (political, media, and public health) agendas influence investors’ trading behavior during COVID-19 infodemic on social media. To what extent do opinion leaders’ social media posts affect the stock market, and do different types of agendas have different effects?
To fill this gap, we select the United States for data collection because of its position as the world’s largest financial market, where market fluctuations may potentially have spillover effect globally. We developed the concept of
agenda diffusion based on agenda-setting. Agenda-diffusion is defined as the dynamic process by which topics or issues of diverse agendas spread and gain prominence across social networks. It investigates the diffusion process of how agendas affect the public, including the types of agendas, dynamic effects, and diffusion mechanisms. (
Brosius et al., 2019;
Weimann & Brosius, 2017). Agenda-diffusion relies on the notion that communication affects social networks (
Weimann & Brosius, 2017). Thus, the dynamic effects of diverse agendas (attention and sentiment) on the stock market represent different diffusion processes on social media platforms.
This study is essential and urgent for several reasons. First, the WHO expressed concerns about online infodemic during the COVID-19 pandemic. This study addresses the infodemic problem from both communication and behavior science perspectives, making valuable contributions to understanding the COVID-19 infodemic. Second, this study introduces the concept of agenda-diffusion to extend the agenda-setting approach, offering a new theoretical approach to explain the COVID-19 infodemic. Finally, this study provides fresh insights into the role of opinion leaders in preventing stock market collapse by analyzing the relationship between indicators of diverse agendas and stock behavior. Thus, this study contributes to the literature and enhances our understanding of agenda-diffusion during infodemic crises, and has important implications for policymakers and researchers alike for intervening agenda (aggregation of influential opinion leaders’ posts) diffusion process in crisis communication to prevent stock market collapse.
COVID-19 pandemic seems to be over, even though the COVID-19 is still present. However, in the future, new pandemics caused by other viruses (bird flu, monkeypox) may emerge. This study provides insights for understanding the relationship between public information and financial traders’ decisions, which may be relevant for future global crises.
In Agenda Diffusion section, we develop an agenda-diffusion approach to address the three limitations of current agenda-setting: setters, dynamic influences, and diffusion processes. We use the agenda-diffusion approach to show COVID-19 agendas on stock trading behavior differs according to the role of opinion leaders (Diverse Opinion Leaders section), dynamic effects (Dynamic Effects section), and diffusion processes (Diffusion Process section).
Results
To analyze the stationarity of the dependent and independent variables, the study employed two tests: the Augmented Dickey–Fuller (ADF) and Phillips–Perron (PP) tests, both of which are designed to detect unit roots in time-series data. According to the results displayed in
Table 1, both the dependent and independent variables were stationary at their respective levels (
p < .05). This indicates a significant level of stationarity and suggests that the time series does not have a unit root, which is a common assumption in many time-series models.
Akaike Information Criterion (AIC) was employed to select lags for the model. This criterion helps determine the optimal number of lags to be included in a time-series model to balance the trade-off between fit and complexity. The study identified that including the lags [3, 0, 1, 0, 4] for the Dow Jones Industrial Average (DJIA), Media Agenda Attention, Political Agenda Attention, Public Health Agenda Attention, and Level of Sentiment, respectively, improved the model. These lags were incorporated because they statistically enhanced the model.
Several diagnostic tests were conducted to assess the robustness of the statistical models presented in this study. The cointegration diagnostics indicates a significant long-term equilibrium relationship between the examined variables. This is evidenced by the F-statistic (5.277), which surpasses the critical value at the 1% level of significance. This finding signifies that the variables in question do not drift apart or converge randomly, but rather move in tandem over time, reflecting a common stochastic trend. This ensures that the variables maintain a consistent relationship with one another over the duration being studied.
In addition to cointegration diagnostics, the Breusch–Godfrey Lagrange multiplier (LM) test and Autoregressive Conditional Heteroskedasticity (ARCH) test were applied to evaluate other potential issues within the model. The LM test result (p = .458) suggests that serial correlation is not a concern, indicating that the residuals of the model are not influenced by past values, which can often lead to inaccurate estimates. Similarly, the ARCH test (p = .057) shows no evidence of heteroskedasticity, indicating that the error variance in the model is uniform across the different levels of the explanatory variables. The absence of serial correlation and heteroskedasticity further substantiates the validity of the model, confirming that it is well-constructed and reliable for the interpretation of the variables’ behavior over time.
Hypothesis 1 (H1) proposed that heightened attention to COVID-19 in the media (H1a) and politics (H1b) would lead to lower stock prices, while increased attention to public health (H1c) would similarly result in a decline in stock values, at the onset of the infodemic. Our findings revealed mixed outcomes. Media attention to COVID-19 shows a significant negative correlation with stock prices (b = −0.040, p < .05), which aligns with H1a. However, political attention reveals an unexpected positive relationship with stock prices at lag (1) (b = 0.114, p < .01) and lag (2) (b = 0.032, p < .05), contradicting H1b. In contrast, public health attention corresponded to a decrease in stock prices (b = −0.080, p < .05), supporting H1c.
Hypothesis 2 (H2) considers the impact of negative sentiment on stock prices at the onset of the infodemic. Our results show that sentiment has a complex relationship with stock prices, with negative sentiment leading to a decrease (b = −0.037, p < .05 in Lag [4]) and an increase (b = 0.060, p < .01 in Lag [3]). These results suggest that increased negative sentiments on the public agenda correlate with a failure (on the third day) and a rise (on the fourth day) in the DJIA. These mixed results partially support H2, indicating that the effect of public sentiment on stock prices may vary over time.
Regarding sentiments, Model 1 in
Table 1 reveals that sentiment has both positive (
b = 0.060,
p < .01 for in Lag [3]) and negative (−0.037,
p < .05 Lag [4]) effects on the DJIA, suggesting that increased negative sentiments on public agenda correlate with a failure (on the third day) and a rise (on the fourth day) in the DJIA, at the onset of the infodemic. Thus, the results partially support H2 that more negative sentiment on public agenda leads to more stock-selling behavior.
Our study proposes Hypothesis 3 (H3) regarding the moderating role of sentiment. However, the interaction terms in Models 2 and 3 were not significant, leading to a lack of support for H3a (media) and H3b (politics). In addition, the interaction term between political agenda attention and sentiment level is significant (b = −0.018, p < .10), indicating that as sentiment becomes more positive, the uplifting effect of political attention on the DJIA weakens. By contrast, when sentiments are more negative, the positive influence of political attention on the DJIA becomes even stronger. Thus, in times of heightened negativity, the stock-boosting effect of political attention is accentuated. Thus, H3c was supported.
Finally, Hypothesis 4 (H4) predicts that increased negative sentiment leads to more media panic, which escalates media hype and triggers lower stock prices.
Table 2 shows the indirect effects: a higher level of sentiment negatively affects the Media Panic Index; a higher Media Panic Index positively affects the Media Hype Index; and a higher Media Hype Index negatively affects the DJIA. Thus, the mediated path “Level of Sentiment ⇒ Media Panic Index ⇒ Media Hype Index ⇒ Dow Jones Industrial Average’ is statistically significant (
b = 0.189,
p < .001, see
Table 3). This finding supports the chain-mediated effect proposed in H4.
Discussion
This study explores how agendas affect stock trading behavior through the public communication of opinion leaders in different fields during the COVID-19 infodemic.
Previous research has emphasized that authoritative and trustworthy news media should release information quicker in times of crisis to counteract information crises and satisfy people’s needs for information (
Evanega et al., 2020;
Eysenbach, 2020;
Naeem & Bhatti, 2020). However, the results for Hypothesis H1a indicate that increased attention to the media agenda leads to lower stock prices. This may be because the previous perspective ignored the fact that the news media’s extensive negative coverage may shape public opinion (
M. McCombs, 2005). When influential people express their views, some news outlets may feel compelled to report their views even though journalists may not agree with them (
Evanega et al., 2020;
Viswanath et al., 2020). Thus, news media may unintentionally contribute to the amplification and mainstreaming of misinformation (
Dhawan et al., 2021). Owing to their high credibility and wide coverage, authoritative media have the potential to exacerbate panic through extensive coverage. This panic may trigger lower stock prices and further increase the risk of stock market collapse.
Contrary to Hypothesis H1b, attention to political agendas was associated with higher stock prices. This finding implies that political agendas pacify investors’ emotions and prevent them from experiencing panic. The reason behind this may be because politicians are the social governors and policymakers. Investors may perceive increased political agenda attention as stability, policy clarity, or some other positive factor. Thus, politicians’ attention may satisfy investors’ expectations of future policies, reduce investor panic, and avoid selling behavior. Indeed, we agree with previous studies that politicians release misleading information based on their political positions (
Evanega et al., 2020). However, from another perspective, this stabilizes the stock market.
Previous studies have suggested that scientific information from public health experts plays an important role in the fight against diseases (
Eysenbach, 2020;
Mourad et al., 2020;
Naeem & Bhatti, 2020;
van Dijck & Alinejad, 2020;
Ye et al., 2021). However, the results for Hypothesis H1c show that increased attention to the public health agenda leads to lower stock prices. This may be related to the fact that scientific information is intended to fight viruses rather than being based on society-wide crisis management. An increase in scientific information may trigger investors to consider experts as emphasizing the dangers of the virus (
Lavazza & Farina, 2020). Dangerous signals from highly reliable experts may accidentally trigger investors to panic and promote selling behavior. In addition, it may also give opportunities to institutional investor that are intentionally selling short. Consequently, public health experts can disrupt the stock market, although this is not their intention. This finding is contrary to those of previous studies that unidirectionally acknowledged the contribution of public health experts; however, we argue that their impact is double-edged.
Results of agenda attention in this study contradict the notion “the more you know, the less you fear” (
López Peláez et al., 2020). Previous arguments have been based on the idea that humans are rational. However, humans, as animals distinguished from machines, are not always rational. Therefore, the more one knows, maybe the more one fears, particularly when the media is presenting contradicting information. On one side, the prevalent fear leads to a wave of selling among irrational (retail) investors, who react impulsively to market uncertainties. Conversely, rational investors, aware of this panic-driven sell-off, often choose to divest ahead of the curve to mitigate losses. In the same vein, institutional investors, who are also rational, exploit this fear-induced volatility. By strategically maneuvering the market, they deliberately lower stock prices to secure profitable positions. Consequently, this multifaceted interplay of investor behaviors contributes to a gradual, step-by-step decline in stock prices.
The results show that while media and health experts’ social media posts negatively impact the stock market, politicians’ posts may have a stabilizing effect. Some key actors and information based on individual-level interactions with investors’ stock trading behavior are consistent with our study. For example, the U.S. House of Representatives Speaker indicated that she would pass the subsequent appropriations and outbreak response bill, to which President Trump reversed his previous opposition and endorsed, triggering a more than 9% rise in the DJIA (
Pramuk, 2020). However, the Wall Street Journal reported that the turmoil associated with the coronavirus could trigger the bursting of the corporate debt bubble and exacerbate the recession (
Lynch, 2020), which led to the DJIA dropping by more than 2,000 points and triggered panic selling. Furthermore, stocks plummeted after the WHO announced the presence of a new variant of the COVID-19 virus (
Stein et al., 2021).
Regarding dynamic effects, the results of Hypothesis H3c reveal that the relationship between political agenda attention and stock prices is conditional on public sentiment levels. This implies that the effect of agenda-related attention on stock prices is influenced by negative biases at the investor’s psychological level. Specifically, in times of prevalent negative sentiment, the positive impact of political attention on stock prices becomes more pronounced, encouraging stock-buying behavior and reducing the likelihood of selling. As the sentiment levels become more positive, the effect of politicians’ social posts on boosting stock prices weakens. This dynamic suggests that politicians are imparted more to investors with negative sentiment levels than to those with positive sentiment levels. During periods of negative sentiment, investors may interpret increased political attention as a sign of stability or policy clarity, which can be seen as a positive factor amid uncertainty during a crisis. This shows that the government/congress is taking the situation seriously and is likely to implement measures to manage the crisis. This perception can lead investors to feel more confident about the political response, which may in turn influence their investment decisions, potentially leading to an increase in stock prices despite the ongoing pandemic.
Previous scholars (
Haroon & Rizvi, 2020) did not investigate how sentiment is transferred step-by-step through the media to the stock market. The results for Hypotheses H2/H4d show the diffusion mechanism of sentiment through a chain of mediation in stock trading behavior. First, negative sentiment triggers media panic, which further triggers increased media hype and, ultimately, negative sentiment leads to stock-selling behavior. Therefore, this study builds on the findings of previous studies to discover the mechanisms and processes of sentiment diffusion. This implies that sentiment on agenda is a diffusion process that affects the stock markets. Sentiments expressed in social media posts can shape the public’s expectations of the future. Excessive negative sentiment can trigger psychological anxiety and worries among investors. This process increases uncertainty about the future and reduces investor confidence. Consequently, this process has the potential to lead retail investors to incur losses and may also create opportunities for institutional investors to engage in short selling in the stock market through this agenda sentiment diffusion pathway. Future crisis management efforts may mitigate the adverse effects of a crisis by intervening in the agenda diffusion process.
Conclusions
This study examined the relationship between various types of opinion leaders’ agendas on social media and stock trading behavior during the COVID-19 information pandemic. The results show that increased attention to COVID-19 in the media and public health agendas triggers stock-selling. By contrast, increased COVID-19 attention to political agendas triggers stock-buying. Furthermore, emotions in public agendas moderate the relationship between attention and stock-trading behavior. Public agenda sentiment triggers stock-selling through a chain-mediated effect. Thus, social media releases by politicians in times of crisis are more effective than media and public health agendas in stopping the stock markets from collapsing.
This study offers insights and guidelines to address the proliferation of infodemic agendas during periods of low sentiment (
Zheng et al., 2018). First, it responds to the WHO’s call for research on infodemics by examining the impact of the COVID-19 infodemic on the stock market. Second, the proposed agenda-diffusion approach provides a novel theoretical perspective for studying infodemic, extending the theoretical and methodological approaches of traditional communication theory. Finally, the findings of this study offer guidance for early intervention strategies to prevent stock market collapses during similar social media events in the future from a communication science perspective.
This study has some limitations that warrant further investigation. First, this study uses a lexicon approach to analyze tweets. Future research may use more advanced models to conduct sentiment analysis, such as machine learning models, to explore the impact of more detailed sentiments (happy, sad, angry, fearful, etc.) on the stock market. Second, an ARDL model was employed to explore the impact of COVID-19 agenda diffusion on stock trading behavior; future research could benefit from using more advanced time-series analysis models to deepen our understanding of this relationship. Third, enriching quantitative data with qualitative insights through mixed methods research could offer a more comprehensive theoretical perspective on the influence of public agendas on market dynamics, particularly when exploring the role of key actors.
Finally, infodemics, which may not be limited to infectious diseases, can manifest in various forms, with one prominent feature being its diffusion as an agenda. For instance, the collapse of the Silicon Valley Bank within 24 hr (
Chowdhury, 2023) illustrates how negative information can influence investors’ herd behavior within a single trading day. As more people engage with this agenda, an ‘infodemic’ forms, which subsequently causes a spillover effect on other institutions following the collapse of one institution. It is essential to understand that no piece of information is innocent during the stock market collapse due to an infodemic. Every snippet of news, no matter how trivial it might seem, can have significant ramifications and contribute to propagation of the infodemic.