What Is The Optimal Number Of Stocks In An Active Portfolio?

As performance dispersion across stocks, sectors, and countries widens in tandem with volatility, professional investors are revisiting the alpha generating capabilities of portfolio managers that prefer to run concentrated portfolios.

The rationale being  that concentrated portfolios allow more flexibility to outperform 'hard to beat' benchmarks. And given the global macro backdrop and resultant alpha opportunities, this could be the right time to relax investment guidelines and put some passive money to work.

But can idiosyncratic risk be diversified away using a limited number of stocks?