The Essentials
At a Glance
- Diversification limits the damage any single holding can do to a portfolio.
- It does not prevent losses when whole markets decline together.
- Concentration builds up quietly, especially through employer stock and big winners.
If a portfolio is diversified, why can it still lose money? People often hear diversification described as protection, then feel misled when a broad market decline pulls everything down at once. The confusion comes from expecting diversification to do a job it was never designed for. It helps to be precise about what it does, and what it does not.
Two kinds of risk
Every investment carries two kinds of risk. The first is specific to that investment: a company's product fails, a borrower defaults, an industry is disrupted, a country's economy stumbles. The second is shared by the market as a whole: a recession, a change in interest rates, a shock that makes investors everywhere less willing to hold risk.
Diversification addresses the first kind. By holding many investments whose fortunes do not rise and fall together, you make it unlikely that any single failure does serious damage. Spread widely enough, specific risk shrinks to a small share of the total.
Market-wide risk is different. It cannot be diversified away by adding more holdings of the same type, because all of them are exposed to it. That risk is, in a sense, the price of admission for the returns that markets have historically provided over long periods.
Diversification protects against the failure of any one thing. It does not protect against the decline of everything.
Spreading across more than companies
The simplest form of diversification is holding many companies instead of a few. But companies in the same industry tend to move together, so holding fifty technology companies is less diversified than it looks. Spreading across sectors, such as health care, energy, finance and consumer goods, adds a second layer.
Regions add a third. Economies do not always expand and contract in step, and currencies move in different directions, so holdings in different parts of the world can behave differently in the same year.
The deepest layer is asset type. Stocks, bonds, cash and, for some investors, real estate or other holdings respond to different forces. In years when stock prices fell because the economy was weakening, high-quality bonds have sometimes held their value or risen, though this relationship is not assured and has varied over time.
What a broad downturn looks like
Suppose, for illustration, an investor holds a portfolio spread across hundreds of companies in many sectors and countries. One company in that portfolio suffers a scandal and its stock falls by half. Because it represents a fraction of one percent of the total, the portfolio barely registers the event. This is diversification working exactly as intended.
Now suppose a recession arrives and stock markets around the world fall by a quarter over several months. The same portfolio, being made mostly of stocks, falls too, perhaps by close to that amount. Diversification across companies did nothing here, because the source of the decline was shared by all of them. Only the portion in bonds and cash offered any cushion.
Both outcomes are the same tool behaving consistently. The first is the problem diversification solves. The second is a problem that only time, asset allocation and temperament can address.
Concentration, including where you work
Concentration is the opposite of diversification, and it tends to accumulate quietly. A stock that has risen sharply becomes a larger share of the portfolio simply by growing. A family business, a piece of real estate or an inheritance can dominate a balance sheet without anyone deciding it should.
Employer stock deserves particular attention. Many people hold shares of the company they work for, through equity compensation, a retirement plan or a purchase program. This ties their savings to the same company that already provides their salary, their benefits and often their professional identity. If the company struggles, income and savings can fall at the same time. The point is not that any particular company is unsafe. It is that even a strong company becomes a single point of failure when it accounts for both a paycheck and a large share of savings.
Reducing a concentrated position can carry tax consequences, and the right approach varies with each situation. This is one of the areas where a qualified tax professional adds real value.
Rebalancing keeps the mix honest
Even a well-diversified portfolio drifts. When stocks rise faster than bonds, the stock share grows, and the portfolio slowly becomes riskier than it was designed to be. Rebalancing is the practice of periodically restoring the intended proportions, typically by trimming what has grown and adding to what has lagged.
Rebalancing is primarily a risk-control practice rather than a way to increase returns, and it can feel counterintuitive, since it means selling some of what has done well. Its purpose is to keep the level of risk where you chose to set it, so that the portfolio you own in a downturn is the portfolio you planned for.
Questions to Discuss With Your Advisor
- Where is my portfolio most concentrated, including employer stock, real estate and any private holdings?
- How would my overall financial picture be affected if my employer's stock fell sharply?
- How much of my portfolio would be exposed to a broad stock market decline, and is that level intentional?
- How often is my portfolio rebalanced, and what triggers it?
