As an investor, should you put all
of your money in one stock or should you spread your bets across many
investments? If it is the latter, how many investments should you have in your
portfolio? The debate is an old one and there are many views but they fall
between two extremes. At one end is the advice that you get from a believer in
efficient markets: be maximally diversfied, across asset classes, and within
each asset class, across as many assets you can hold: the proverbial “market
portfolio” includes every traded asset in the market, held in proportion to its
market value. At the other is the “go all in” investor, who believes that if
you find a significantly undervalued company, you should put all or most of
your money in that company, rather than dilute your upside potential by
spreading your bets.
Cuban versus Bogle
These arguments got media attention recently, largely because two high-profile investors took opposite positions. The first salvo was fired by Mark Cuban, who made his substantial fortune (estimated by Forbes to be $2.5 billion in 2011) as an entrepreneur who founded and sold Broadcast.com for $ 6 billion by Yahoo!, at the peak of the dot com boom. Cuban's profile has increased since, largely from his ownership of the Dallas Mavericks, last year's winners of the NBA championship, and his
intemperate outbursts, about referees, players and the NBA in general. With typical understatement, Cuban
claimed that diversification is for idiots and that investors, unless they have access to information or deals, should hold cash, since hedge funds have such a tremendous advantage over them. In response, John Bogle, the father of the index fund business, countered that "the math (for diversification) has been proved over and over again. It's not just the first thing an investor should think about, but the second, the third and probably the fourth and the fifth thing investors should think about".
The
limiting cases
So, should
you diversify? And if so, how much should you diversify? The answers to these
questions depend upon two factors: (a) how certain you feel about your
assessment of value for individual
assets (or markets) and (b) how certain you are about the market price
adjusting to that value within your specified time horizon.
·
At one limit, if you are absolutely certain
about your assessment of value for an asset and that the market price will
adjust to that value within your time horizon, you should put all of your money
in that investment. Though this may seem like the impossible dream, there are
two possible scenarios where it may play out:
o
Finite life securities (Options, Futures and
Bonds): If you find an option trading for less than its exercise value: you
should invest all of your money in buying as many options as you can and
exercise those options to make a sure profit. In general, this is what falls under the umbrella of pure arbitrage and it is feasible only
with finite lived assets (such as options, futures and fixed incomes
securities), where the maturity date provides a endpoint by which time the price
adjustment has to occur.
o
A perfect tip: On a more cynical note, you
can make guaranteed profits if you are the receipient of inside information
about an upcoming news releases (earnings, acquisition), but only if there is
no doubt about the price impact of the release (at least in terms of direction)
and the timing of the news release. (Rumors don’t provide perfect information
and most inside information has an element of uncertainty associated with it.)
The problem, of course, is that you would be guilty of insider trading and may end up in jail... .
·
At the other limit, if you have no idea what
assets are cheap and which ones are expensive (which is the efficient market
proposition), you should be as diversified as you can get, given transactions
costs. If you have no transactions costs, you should own a little piece of everything. After all, you gain nothing by holding back on diversification and your
portfolio will be deliver less return per unit of risk taken.
Most active investors tend to fall between these two
extremes. If you invest in equities, at least, it is inevitable that you have
to diversify, for two reasons. The first is that you can never value an equity
investment with certainty; the expected cash flows are estimates and risk
adjustment is not always precise. The second is that even if your valuation is
precise, there is no explicit date by which market prices have to adjust; there
is no equivalent to a maturity date or an option expiration date for equities.
A stock that is under or over priced can stay under or over priced for a long time, and even get
more under or over priced.
There is one final point worth making. Note that how much you diversify will be based upon your perceptions of the quality of your valuations and the speed of market adjustment, but perceptions are not reality. In fact, psychologists have long noted (and behavioral economists have picked up the same theme) that human beings tend to have too much confidence in their own abilities and too little in the collective wisdom of the rest of the world. In other words, we tend to think our valuations are more precise than they really are and that the market adjustment will occur sooner than it really will.
How diversified should you be?
Building on
the theme that diversification should be attuned to the precision of your valuations and the speed of market adjustment, the degree to which you should diversify will depend upon how your
investment strategy is structured, with an emphasis on the following
dimensions:
a. Uncertatinty
about investment value: If your investment strategy requires
you to buy mature companies that trade at low price earnings ratios, you may
need to hold fewer stocks , than if it requires you to buy young, growth
companies (where you are more uncertain about value). In fact, you can tie the
margin of safety (referenced earlier in this chapter to how much you need to
diversify; if you incorporate a higher margin of safety into your investing, you should feel
more comfortable holding a less diversfied portfolio. As a general propostion, your response to more uncertainty should be
more diversification, not less.
b. Market
catalysts: To make money, the market price has to adjust towards your
estimated value. If you can provide a catalyst for the market adjustment
(nudging or forcing the price towards value), you can hold fewer investments
and be less diversifed than a completely passive investor who has no choice but
to wait for the market adjustment to happen. Thus, you will need to hold fewer
stocks as an activist investor than as an investor who picks stocks based upon
a PE screen. Ironically, this would mean
that the more inefficient you believe markets are, the more diversified you
will need to be to allow for the unpredictability of market movements.
c.
Time horizon: To the extent that the
price adjustment has to happen over your time horizon, having a longer time
horizon should allow you to have a less diversified portfolio. As your liquidity needs rise, thus shortening your time horizon, you will have
to become more diversifed in your holdings.
In summary, then, there is nothing irrational about holding
just a few stocks in your portfolio, if they are mature companies and
you have built in a healthy margin of safety, and/or you have the
power to move markets. By the same token, it makes complete sense for other
investors to spread their bets widely, if they are investing in young, growth
companies, and are unclear about how and when the market price will adjust to value.
So, the choice is not between diversification and active investing, since
you can pick stocks and be diversified at the same time. It should be centering on making the
right decision on how much diversification works for you,.
Evidence from the field
So, how
diversified is the typical investor’s portfolo? And if it is relatively
undiversified, is it undiversifed for the right reasons? And what is the payoff or cost to being undiversified? The evidence from many
studies over the last decade or so is enlightening:
- Investors are thinly diversified: The typical
investor is not well diversified across either asset classes, or within each
asset classes, across assets. A study of 60,000 individual investor portfolios
found that the median investor in this group (which was a representative sample
of the typical active investor in the United States) held three stocks and that
roughly 28% of all investors have portfolios composed of one stock. In a later study, the same authors find that not only do investors hold relatively few stocks but that these stocks tend to be highly correlated with each other (same sector or type of stock).
- Many are thinly diversified for the wrong
reasons: While the lack of diversfication can be justified if you have good
information or superior assessments of value, many of the undiversfied
investors in this study failed to diversfy for the wrong reasons. On average,
not only did younger, poorer less eductated investors diversify less, but they, as
a group, tend to be over confident in their abilities to pick stocks.
- And they pay a price for being thinly
diversified: Not surprisingly, investors who fail to diversify because they are
over confident or unfamiliar with their choices pay a price. On average, they
earn about 2.40% less a year, on a risk adjusted basis, than their more
diversified counterparts.
- But some undiversified investors are good stock pickers: On a
hopeful note, there are clearly some active investors who hold back on
diversification for the right reasons, i.e., because they have better
assessments of value for stocks than the rest of the market and long time
horizons. A study of 78,000 household portfolios finds that the among households wealthy enough to be diversified, those with more concentrated portfolios (holding one or two stocks) earn higher returns than those with more diversified portfolios (holding three or more stocks) by about, though they are also more volatile. The study goes on to note that the higher returns can be attributed to stock picking prowess and not to market timing or inside information.
Bottom line
Most investors are better off diversifying as much as they
can, investing in mutual funds and exchange traded funds, rather than
individual stocks. Many investors who choose not to diversify do so for the wrong reasons (ignorance, over confidence, inertia) and end up paying dearly for that mistake. Some investors with superior value assesssment skils,
disciplined investment practices and long time horizons can generate superior
profits from holding smaller, relatively undiversified portfolios. Even if you believe that you are in that elite group, be careful to not fall prey to hubris, where you become over
confident in your stock picking and market assessments and cut back on
diversification too much.