Correlation coefficients between the LPPEIIPA and EASMI for the period 1948–2014. The values in parentheses represent the 9-yr low-pass and high-pass time series, respectively, which may represent the decadal and interannual components of a variable. The correlation coefficients significant at the 99% confidence level using the Student’s t test are in boldface. The significance of the correlation between two low-pass time series was assessed using the effective number of degrees of freedom (Bretherton et al. 1999).