Correlation Among Stock Index Returns

Correlation among stock Index Returns can be defined as the extent to which the values of different types of investments move in tandem with one another in response to changing economic and market conditions. Correlation determines how related the rates of returns on indices are. Correlation is measured on a scale of -1 to +1. Investments with a correlation of +0.5 or more tend to rise and fall in value at the same time. Investments with a negative correlation of -0.5 to -1 are more likely to gain or lose value in opposing cycles.

The study of S&P indices and MSCI Indices show that over the past five years, the various equity markets around the globe have seen an increase in correlation. While the S&P 500 index, the MSCI EAFE index, the MSCI Emerging Market index, the S&P MidCap 400, and the S&P SmallCap 600 index have all posted positive trailing five-year total returns, the magnitude of the gains has varied widely. While the "500" has returned 9.5% annually over the past 5 years (through May 7), the MSCI EAFE index and the MSCI EM index have returned 17.2% and 25.9%, respectively, highlighting their powerful portfolio diversification benefits. Similarly, the S&P MidCap 400 index and the S&P SmallCap 600 index have posted returns of 12.5% and 12.6%, respectively, thereby adding value to a diversified portfolio. Hence, despite increasing directional correlation, the inclusion of a wide array of equity asset classes has significantly benefited portfolio performance.