Fig. 3
Abrupt transitions in financial stock indices. Applying our approach to three stock index datasets a DAX, b NASDAQ-100, and c S&P BSE SENSEX, we identify three major epochs centered around the ‘mortgage crisis’, ‘Eurozone crisis’, and the ‘Grexit’/‘Brexit’ crises, as seen from the normalized Google trends data in (d). In each epoch we see a high number of statistically significant dynamical shifts at α = 0.05 and these periods are interspersed with quiescent periods with far fewer of such shifts. Additional pink squares in (d) correspond to: (1) BSE SENSEX crash of 22 May 2006, (2) bankruptcy claim by Lehman Brothers on 15 September 2009, (3) Indian parliamentary elections from 7 April to 12 May 2014, and (4) SENSEX crash (1600 points) of 24 August 2015. The horizontal dashed lines in (a–c) indicate the confidence level α = 0.05 of the statistical test. However, when multiple comparisons are taken into account (see Methods), only a subset of p-values below 0.05 are found to be significant (shown here with plus signs)
