This study develops a comprehensive methodological framework for identifying and quantifying investor echo chambers in online stock discussion forums. Motivated by a dynamic model of endogenous echo chamber formation, which formalizes how investors optimally allocate attention and update beliefs under cognitive and informational constraints, we construct a two-layer multiplex investor network that integrates common-attention similarity and semantic similarity to jointly capture the informational and cognitive linkages among investors. This framework enables the systematic examination of how shared information sources and convergent opinions emerge within investor communities. We compute both community-level and individual-level (node-level) echo-chamber intensity by integrating measures of social homophily, semantic reinforcement, and community insularity. At the firm level, we further aggregate these micro-level indicators using attention-weighted indices, community concentration (HHI), and semantic polarization metrics to characterize how echo-chamber dynamics manifest in firm-related discussions. In addition, we propose a general empirical panel framework to examine the relationship between investor echo-chamber intensity and firm-level outcomes. Overall, this paper provides a methodological foundation for the broader Investors’ Echo Chamber Project, offering scalable tools for network-based behavioral analysis and laying the groundwork for future research linking online social dynamics, financial market efficiency, and corporate decision-making.

This study documents a novel, culturally embedded calendar anomaly in the Shanghai Composite Index (SSE Composite) derived from the Nayin (纳音) Five Elements system—a traditional Chinese sexagenary calendrical framework. Utilizing daily data from 1990 to 2025, the analysis reveals a significant correlation between elemental two-year periods and market performance. Key findings include: Earth-Element Dominance: Earth periods exhibit a 100% positive return rate (4/4) with a mean return of +123.4%. The effect size is substantial (Cohen’s d=1.50) compared to non-Earth periods. Metal-Element Declines: Metal periods universally display a structural peak-and-decline morphology, with an average −30.4% late-cycle decline. Water-Element Momentum: Water periods systematically mirror the directional momentum of their predecessors with 100% accuracy (3/3). These patterns fail to replicate in the S&P 500, suggesting a unique cultural-behavioral channel where traditional metaphysical cycles modulate investor sentiment in the Chinese market. This research provides the first empirical validation of Nayin-based cyclicality in financial asset pricing, offering a predictive framework for institutional and individual investors focused on the China-specific market. Keywords: Calendar anomaly, Chinese traditional calendar, Nayin Five Elements, Shanghai Composite Index, Cultural behavioral finance, Sexagenary Cycle, Market Sentiment Declaration of Interest The author declares no conflict of interest. To ensure the objectivity of this research, the author further declares that he holds no active personal trading positions in the securities discussed. The author's personal trading account has been inactive with zero transactions over the past five years.

Utilizing microevaluation data on the extent to which firms advance the achievement of the UN’s Sustainable Development Goals (SDGs) provided by Robeco, this paper examines the influence of corporate sustainability on stock price performance and its underlying economic mechanisms. The empirical results suggest that firms’ sustainability has a significant negative effect on excess returns, particularly the contribution of firms to the social dimension of sustainability. Firms’ SDG performance can alleviate financing constraints and reduce financial risk, but it does not significantly enhance financial performance, leading to market capital outflows from high SDG-performing firms, especially from individual investors. Furthermore, our results suggest that high SDG-performing firms are undervalued and do not increase the information content in their stock prices, which may be the main reason for the negative effect of SDG performance. We also conduct a series of heterogeneity tests, which show that firms from regions with high environmental regulatory intensity and less economic development, as well as heavily polluting firms and firms with poorer information environments, experience greater negative effects. These findings have implications for investors to properly understand corporate sustainability and for regulators to promote the development of a low-carbon economy.

Using Chinese publicly listed firms from 2007 to 2020, this study empirically explores the impact of non-controlling shareholders’ network on the corporate excess goodwill. We find that the centrality of non-controlling shareholders’ network significantly decreases the excess goodwill from mergers and acquisitions, indicating that non-controlling shareholders’ network can restrain the goodwill bubbles. Moreover, the inhibitory effect of non-controlling shareholders’ network on excess goodwill stems from pressure-resistant institutional investors and individual investors. This effect is achieved through the information effect, resource effect, and governance effect. Furthermore, this inhibitory effect is more pronounced in firms located in less developed regions and legal environments, and firms with lower audit quality. In conclusion, non-controlling shareholders’ network plays a positive role in the restriction of excess goodwill in listed companies.

This paper shows that a New Year’s gambling preference of individual investors impacts prices and returns of assets with lottery features. January call options, especially the out-of-the-money calls, have higher retail demand and are the most expensive and actively traded. Lottery-type stocks outperform their counterparts in January but tend to underperform in other months. Retail sentiment is more bullish in lottery-type stocks in January than in other months. Furthermore, lottery-type Chinese stocks outperform in the Chinese New Year’s Month but not in January. This New Year effect pro- vides new insights into the broad phenomena related to the January effect.

Using data from 11 major international markets that celebrate six cultural New Year holidays that do not occur on January 1, we find that stock markets tend to outperform in days surrounding a cultural New Year. After controlling for firm characteristics, an average stock earns 2.5% higher abnormal returns across all markets in the month of a cultural New Year relative to other months of the year. Further evidence suggests that positive holiday moods, in conjunction with cash infusions prior to a cultural New Year, produce elevated stock prices, particularly among those stocks most preferred and traded by individual investors.

This study investigates the impact of non-controlling shareholders' network on corporate excess goodwill using Chinese publicly listed companies from 2007 to 2020. We find that a stronger centrality of non-controlling shareholders' network leads to a significant decrease in excess goodwill resulting from mergers and acquisitions. This implies that the non-controlling shareholders’ network has a significant inhibitory effect on the occurrence of goodwill bubbles. Mechanism analysis finds that non-controlling shareholders' network can inhibit excess goodwill thorough information effect, resource effect, and governance effect. Furthermore, this inhibitory effect is attributed to pressure-resistant institutional investors and individual investors, and is more pronounced in firms located in less developed intermediary market and legal system environment, as well as firms with lower audit quality. In summary, the non-controlling shareholders' network plays a positive role in curbing excess goodwill in listed companies.

By using a unique proprietary dataset and implementing the Wuhan (China) lockdown from January to April 2020 as a natural experiment, we find that individual mutual fund investors in Wuhan significantly reduced their trading frequency, total investment of their portfolios, and risk level of their invested funds during the lockdown period as compared to investors in other cities. These changes are stronger for older investors and are reversed soon after the lifting of the lockdown. Our results suggest that the elimination of face-to-face interaction among individual investors reduced their information sharing, which led to more conservatism in their financial trading. These results are not supported by the alternative explanations of limited investor attention and temporary changes in personal circumstances, including depression and/or income reduction, during the lockdown period. Finally, consistent with the theory of naïve investor trading, we also find that investors received higher trading returns during the lockdown.

Using four datasets of individuals’ digital payment and mutual fund investment records from a dominating fintech platform, we observe a robust U-shaped relation between individuals’ consumption and their financial wealth shocks. Contrary to the prediction of the wealth effect, individuals increase their consumption shortly after experiencing large positive and negative wealth shocks. The unexpected increase in consumption following negative wealth shocks is particularly pronounced among consumption categories with a “hedonic” nature, such as entertainment-related items. We show that this effect, termed “financial retail therapy,” is consistent with a dynamic model of Prospect Theory and evidence from a controlled laboratory experiment.

We examine how stakes affect investor behaviors. In our unique setting, the same investors trade stocks in real accounts using their own money and, at the same time, trade in a simulated setting. Our real-world within-investor estimation produces strong evidence that investors exhibit stronger biases and perform worse in their higher-stakes real accounts than in their lower-stakes simulated accounts. Even with no monetary stakes, investors exhibit strong biases in their simulated accounts, and biases in the two types of accounts are strongly positively correlated. Such behavioral consistency suggests that low-stakes experimental methods, although imperfect, can be informative about real-world human behaviors. Using account data from two brokerage companies, we find that investors exhibit a stronger disposition effect on positions with greater portfolio weight. Hence, the finding that stakes-strengthening-biases may not be unique to the comparison between no-monetary and high-monetary stakes.