brown eggs on brown wooden bowl on beige knit textile

Should you have more baskets to store your eggs? Is more always better?

You’ve probably heard the saying “Don’t put all your eggs in one basket”. The wisdom goes that at least if you drop the basket, you won’t have to worry about losing all your eggs.

In the investing world, the same logic can apply. Having a portfolio of many stocks means that if one company fails, bringing the value of its stock down with it, an investor’s portfolio should not be affected to a large degree. In the finance literature, this is known as eliminating non-systemic risk.

In general, portfolios with 10 or more stocks reduce the amount of volatility dramatically relative to the market and once the portfolio reaches 30 or more stocks, volatility is reduced to barely above a percentage point. (see here)

Unfortunately, there are a few problems with just having a larger number of stocks in your portfolio.


Industry-specific Risk

It doesn’t matter if you have many stocks if they all belong to the same industry and that industry is currently in the midst of a cyclical decline or the various players in the industry were all engaged in unsavoury practices.

In 2008-2009, the financial industry was hit by the downturn in the U.S. housing market. This led to credit being frozen in the banking sector and once the dominoes fell, even the better-capitalised banks felt some pain.

More recently, many Singapore-listed firms in the oil & gas sector were also hit when oil prices fell from over a hundred US dollars to a low of 30 US dollars. The bigger players such as Keppel Corp and SembCorp saw their share prices fall to multi-year lows and haven’t recovered much despite oil prices climbing up to about 70 US dollars.

Smaller companies that provided services to the offshore gas industry suddenly found demand for their services dry up and those that were up to their eyeballs in debt have been in serious trouble for some years now.

In short, having a large number of stocks doesn’t matter if a large number of them all depend on the same economic factors for profit.


Geographic or Location Risk

The same goes for companies that all depend on a certain location for profit. It’s also well-known that investors tend to have a home-bias. This means that investors tend to put a huge chunk of their portfolio in their home country.

If the country has a huge domestic economy and many of the companies are dependent on that country for business, then when the economy goes south, the fortunes of those companies will all be affected.

Similarly for the stock market, having all your stocks in a single market could mean terrible returns. from 1999-2009, investors in the S&P 500 would have made less than 0% returns p.a. This is the “lost decade” that many investment books talk about.

What those books neglect to mention is that the “lost decade” happened for the S&P 500. Other asset classes within the U.S., as well as markets outside the U.S., fared much better. For example, the MSCI EM Emerging Markets (Net) Index returned 9.78% in annual total returns for the same period.


Where Conventional Diversification Fails

So, if you diversified across a number of stocks, industries, and markets, you should be fine right?

Not so fast.

Research has shown that when a crisis hits, many asset classes that seem uncorrelated start seeing their correlations move to one:

But it has been well documented that correlations tend to increase in down markets, especially during crashes (i.e., “left-tail events”). Studies have shown this effect to be pervasive for a large variety of financial assets, including individual stocks, country equity markets, global equity industries, hedge funds, currencies, and international bond markets.

To make matters worse, research also finds that:

Not only did correlations increase on the downside, but they also significantly decreased on the upside. This asymmetry is the opposite of what investors want. Indeed, who wants diversification on the upside? Upside unification (or antidiversification) would be preferable. During good times, we should seek to reduce the return drag from diversifiers.

In other words, different asset classes may move out of step in bull markets while they all seem to move in the same direction when the bear bites. This results in diversification that causes a drag on returns in bull markets while offering little protection from the bear.

However, the article also finds that the two asset classes that are useful for diversification are a mix of Stocks and Bonds. Specifically, the study used Treasuries in the bond mix which suggests that Treasuries go up when Stocks go down due to a flight to safety.


Main Takeaways

The main lessons from this are to be aware that while diversification is necessary within the asset class, we don’t want to add too many asset classes to the mix thinking that that will be the solution to preventing the entire portfolio from tanking at the same time. The bigger lesson would be to have a sense of whether valuations are rich or cheap as well as to rebalance the portfolio towards the optimal mix.

Alternatively, you can take Andrew Carnegie’s advice to “put all eggs in one basket and watch that basket” but I wouldn’t recommend it; It’s too much work. Furthermore, it’s hubris to think that you are better than many of the people who analyse companies for a living. This may work for investors like Warren Buffett* but unless you think that you’re that good, you should spread your investments.

Just don’t spread them too thin.



*Actually, even Warren Buffett had his share of mistakes like Dexter’s Shoes so imagine if all he owned was that shoe company.