Having reviewed Dynamo's links
Hi Dynamo
I studied those three links in some detail and they support me in my views that 10 stocks is enough.
I found
Bernstein's article on diversification the most informative.
My big problem with these studies is that they define risk as volatility, so I got excited when I came across the following paragraph in Bernstein: <!--EZCODE QUOTE START--><blockquote>
Quote:<hr> This is all profound and important stuff. And, unfortunately, highly misleading. …
There are critically important dimensions of portfolio risk beyond standard deviation... <hr></blockquote><!--EZCODE QUOTE END-->
So I expected to see my idea supported and then he goes on to conclude that you need 200 stocks to minimise risk! He is defining risk as the risk of underperforming the market!!!!
He selected 98 portfolios of 15 stock in 1989 and looked at their returns after 10 years. The S&P returned 19% during those 10 years. So how bad was the worst of the 98 selections? The worst was 14%. Two produced <!--EZCODE ITALIC START-->
only<!--EZCODE ITALIC END-->15%.
Coming last in a sample of 98 is a disaster if you are a fund manager. You will get a name for being a dog. But earning 14% a year for 10 years is not a bad result.
A further quote:
<!--EZCODE QUOTE START--><blockquote>
Quote:<hr> DIVERSIFICATION: (WSJ) Ronald Surz and Mitchell Price calculated returns for portfolios of 15 randomly selected stocks over the 13½ years through June 1999.
The authors found that among such randomly selected 15-stock baskets, the typical portfolio strayed as much as 8.1 percentage points a year from the market's return. Thus, if the market was up 11% in a given year, the typical portfolio might gain as much as 19.1% -- or as little as 2.9%. <hr></blockquote><!--EZCODE QUOTE END-->
This seems to suggest that in a year, the worst basket underperformed by 8%. I don't think that underperforming the market is a catastrophic consequence.
<!--EZCODE BOLD START-->
So to summarise my views:<!--EZCODE BOLD END-->
By <!--EZCODE ITALIC START-->
risk<!--EZCODE ITALIC END--> I mean, the chance that something catastrophic might happen. A permanent loss of long-term value would count as catastrophic. Underperforming the market or short-term volatility do not count as risk in my book.
You cannot eliminate risk.
Deposit accounts will probably decline by 50% in real value over the longer term - that is real and substantial risk.
A diversified stockmarket investment will probably beat inflation and the return on deposits over the longer term. <!--EZCODE BOLD START-->
I was wrong<!--EZCODE BOLD END--> to convey the impression that there is no risk in such a strategy - but it is the least risky strategy.
Is 10 shares enough? Yes, I still think it is. The market risk is much higher than the stock selection risk from having only 10 shares.
Is an Irish portfolio suitably diversified? I am still thinking about this.
Brendan