Figure 3. Correlations between daily mentions of a company's name and transaction volumes for the company's stock.

For each of the 31 companies that were listed in the Dow Jones Industrial Average between 2^nd January 2008 and 31^st December 2012, we plot the Spearman's rank correlation between the daily number of mentions of a company's name and the transaction volume of the corresponding company's stocks. Companies are indicated using their ticker symbol, for which a full list can be found in the Supplementary Information (Table S1). We analyze the distribution of correlation coefficients and find that, overall, the correlation coefficients are significantly higher than zero (median correlation coefficient = 0.074; mean correlation coefficient = 0.100; W = 450, p < 0.001, Wilcoxon signed rank test). In other words, the daily number of mentions of a company's name is positively correlated with the daily transaction volume of a company's stocks.