Mar 18, 2009
Q & A
Is diversification working today, when we need it most?

EFF/KRF: When overall market volatility increases, idiosyncratic (security-specific) volatility also tends to increase. For example, market volatility is currently quite high, and the dispersion of the cross section of stock returns (which is idiosyncratic volatility) is also unusually high. Diversification has no effect on the volatility of the overall market, but it reduces the effect of idiosyncratic volatility on a portfolio's return. To put it differently, active investment is a riskier strategy when volatility is high because active portfolios are, almost by definition, poorly diversified.

In short, diversification is now more important than usual.

ABOUT FAMA AND FRENCH
Eugene F. Fama
The Robert R. McCormick Distinguished Service Professor of Finance at the University of Chicago Booth School of Business
Kenneth R. French
The Carl E. and Catherine M. Heidt Professor of Finance at the Tuck School of Business at Dartmouth College
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