What’s the right amount? During the 1960s, most financial advisers believed that 12 to 30 stocks were necessary for diversification. Well-known economist Burton Malkiel, author of the classic A Random Walk Down Wall Street, concluded that this amount of stocks could eliminate most of the element of risk from a portfolio. (At this time, “risk” was defined as the chance of suffering big swings away from the average market return.) Interestingly, in 2001, Malkiel found that it took 50 stocks to get the risk reduction that 20 used to provide. Similarly, in a recent Seekingalpha.com article, Roger Nussbaum wrote: “If you can accept that anything can fail, then the issue of position sizing becomes critical. This has been covered here many times in terms of targeting individual stocks at 2% to 3% of the portfolio as many others go with larger weightings for their holdings. Getting caught in something that fails is not the worst thing that can happen to an investor because it can happen to any company. It is bad to get caught with 10% of the portfolio in something that fails, and this happens.”So both Malkiel and Nussbaum are in the camp that says you need somewhere between 30 to 50 different stocks. My own personal preference is in the 30 range. Most investors can’t keep track of 50 stocks. With 30 you can still know what is going on at each company, but you have enough diversity to lower portfolio volatility. Nonetheless, whether it’s 30 or 50, I think we all agree that 150 is way too much!aaron@lighthousecapital.co.il
Aaron Katsman is a licensed financial adviser in Israel and the United States who helps people with US investment accounts.