Although stock or indexselection is generally based on volatility characteristics and the size of specific equities, low volatility ETFs, de facto have sector concentrations investors should keep in mind when they are making their selections.
This hypothesis was the force behind the creation of index funds that were designed to simply replicate the returns of major indexes without intelligent stock selection.
Academic estimates are that these statistical biases of self-selection (reporting is optional for the largely unregulated hedge fund industry) add 3-5 percentage points to index returns.