Stock investors face the perennial challenge of deciding how many stocks to own in their portfolios. While there is no right answer and it will vary across individuals and time, it is one of the most important decisions in determining investment outcomes. Simply put, the  crucial ‘diversification versus concentration’ debate is one that no investor can avoid. Many of those who favour the concentration side in this debate cite the data from the widely followed eVestment database of professionally managed equity portfolios. This shows that concentrated portfolios (35 or fewer holdings) outperform larger, non-concentrated portfolios (over 35 holdings) over long…