Surely by now you will have heard the term “diversification” being used when talking about investing. However, a less well known buzz-word, “diworsification” is important to know as well. Personally, I first came across this term in one of Peter Lynch's books, which is ironic considering some have said that he never met a stock he didn't like – which is in reference to his Magellan fund holding more than 1,000 holdings at one time.
(Lynch originally used the term “diworsification” to describe a company that expanded into businesses beyond their core competencies, but “diworsification” can be extended to an investor's portfolio as well, which is the focus of this discussion.)
Diworsification refers to the fact that you can diversify too much. For example, if you own one company's stock you could potentially hit it big, but you could also lose it all. If on the other hand, you owned 100 companies (in equal weight) and one company went bust or doubled overnight, the net impact to your portfolio is only +/- 1%. Further, if you owned 1,000 stocks and one company either tanked or doubled, the effect on your portfolio is only +/- 0.1%.
The premise is that as a stock picker, naturally you would select the stock with the best prospects first, and then the second best, the third best, etc. But at what point do you get to the 'n'th stock that has a lower return prospect than the market average? Or put another way, at what point are you just adding holdings to your portfolio for the sake of adding holdings, with the new addition's potential return creating a drag on your overall portfolio's return? If you hold too many securities then the winners won't have a significant impact on your portfolio's performance (nor would the losers). You might as well hold everything without giving it any further thought (i.e., perhaps using an ETF).
Many times I have seen an investor with five different mutual funds from five different fund companies and all of them invest in Canadian equities – there is significant overlap in the holdings and yet the investor might think they have diversified since they have five mutual funds instead of one. More prudent would be to have one Canadian equity fund and then some funds that invest internationally as well, and perhaps a fixed income fund to temper volatility.
If you invest using ETFs which may provide broad market coverage and have hundreds of individual stock holdings, you don't need to worry about diworsification within the ETF – the mandate is not to beat the market, but rather to track the benchmark index as closely as possible less a very small fee, which they do wonderfully well. But if you are using actively managed money (funds or individual stock picking) and your goal is to beat the market, then you might be interested in gauging any possible diworsification.
Warren Buffett once said that an investor should be given a punch-card with 20 spots on it. Any buy or sell transaction would cost you one of the twenty spots on your card. Once you got to 20 – that's it, no more transactions. (This is not per year, but rather for your entire life.) If you did that, you would probably take more time to understand your investments, and be better off because of it. You certainly wouldn't be accused of diworsification either.