Cashtag piggybacking: uncovering spam and bot activity in stock microblogs on Twitter

Microblogs are increasingly exploited for predicting prices and traded volumes of stocks in financial markets. However, it has been demonstrated that much of the content shared in microblogging platforms is created and publicized by bots and spammers. Yet, the presence (or lack thereof) and the impact of fake stock microblogs has never systematically been investigated before. Here, we study 9M tweets related to stocks of the 5 main financial markets in the US. By comparing tweets with financial data from Google Finance, we highlight important characteristics of Twitter stock microblogs. More importantly, we uncover a malicious practice - referred to as cashtag piggybacking - perpetrated by coordinated groups of bots and likely aimed at promoting low-value stocks by exploiting the popularity of high-value ones. Among the findings of our study is that as much as 71% of the authors of suspicious financial tweets are classified as bots by a state-of-the-art spambot detection algorithm. Furthermore, 37% of them were suspended by Twitter a few months after our investigation. Our results call for the adoption of spam and bot detection techniques in all studies and applications that exploit user-generated content for predicting the stock market

Investor Sentiment in Japanese and U.S. Daily Mutual Fund Flows

We find evidence that is consistent with the hypothesis that daily mutual fund flows may be instruments for investor sentiment about the stock market. We use this finding to construct a new index of investor sentiment, and validate this index using data from both the United States and Japan. In both markets exposure to this factor is priced, and in the Japanese case, we document evidence of negative correlations between Bull' and Bear' domestic funds. The flows to bear foreign funds in Japan display some evidence of negative correlation to domestic and foreign equity funds, suggesting that there is a foreign vs. domestic sentiment factor in Japan that does not appear in the contemporaneous U.S. data. By contrast, U.S. mutual fund investors appear to regard domestic and foreign equity mutual funds as economic substitutes.

PSI-20 fluctuation : correlation of the portuguese stock market with major global capital markets

In this paper, we will analyze the increase of correlations in the market during periods of crisis, due to its paramount importance to the management and optimization of the portfolio, and especially for risk diversification in portfolio management. An evaluation of the level of correlation between the stock markets is important for several reasons. First, it enables to evaluate changes in the patterns of correlation, and thus to make the proper adjustments in portfolios’ investment. Second, policy makers are also interested in these correlations because of its implications for the stability of the financial system. The correlation coefficients are biased measures of dependence when markets become more volatile. This paper explores the correlation of the Portuguese capital markets with the Asian, American, European and Latin American Spanish stock markets. To this end, we used the PSI-20 index, Nikkei 225, NASDAQ, S&P 500, Euronext 100 and Ibex-35. Our analysis results show that the correlation does exist as a phenomenon during financial crises (Bear Market), reducing the benefits of portfolio diversification when most needed. Moreover, we believe that correlations have increased between the markets in recent years.N/

Stock market interactions and the impact of macroeconomic news – evidence from high frequency data of European futures markets

This study analyzes the short-term dynamic spillovers between the futures returns on the DAX, the DJ Eurostoxx 50 and the FTSE 100. It also examines whether economic news is one source of international stock return co-movements. In particular, we test whether stock market interdependencies are attributable to reactions of foreign traders to public economic information. Moreover, we analyze whether cross-market linkages remain the same or whether they do increase during periods in which economic news is released in one of the countries. Our main results can be summarized as follows: (i) there are clear short term international dynamic interactions among the European stock futures markets; (ii) foreign economic news affects domestic returns; (iii) futures returns adjust to news immediately; (iv) announcement timing of macroeconomic news matters; (v) stock market dynamic interactions do not increase at the time of the release of economic news; (vi) foreign investors react to the content of the news itself more than to the response of the domestic market to the national news; and (vii) contemporaneous correlation between futures returns changes at the time of macroeconomic releases. JEL Classification: G14, G1

Where does Volatility and Return Come From? The Case of Asian ETFs

We analyze return and volatility of Asian iShares traded in the U.S. The difference in trading schedules between the U.S. and Asia offers a unique market setting that allows us to distinguish various return and volatility sources. We find Asian ETFs have higher overnight volatility than daytime volatility, explained by public information released during each local market’s trading session. Local Asian markets also play an important role in determining each Asian ETF return. Nonetheless, returns for these funds are highly correlated with U.S. markets, indicative of the effects of investor sentiment and location of trade. Finally, returns in the U.S. market Granger-cause returns in all six Asian markets analyzed.International ETF; iShares; returns; variance; diversification