Investing in a single company, industry, or type of asset can expose your portfolio to risks that may be difficult to predict.
Diversification is a strategy for spreading investments across different securities, asset classes, industries, and geographic markets so that the performance of one investment does not determine the outcome of your entire portfolio.
The purpose of diversification is not to eliminate investment risk. It cannot prevent losses when broad markets decline. Instead, diversification can reduce the impact of risks that are specific to a particular company, sector, asset class, or market.
For example, owning shares of several companies in different industries may reduce the damage caused by one company’s poor performance. Holding investments across different asset classes may provide another layer of diversification.
However, simply owning many investments does not automatically create a diversified portfolio. Ten technology stocks, for example, may still leave an investor heavily concentrated in one sector.
In this guide, you’ll learn:
- What investment diversification actually means
- Why diversification can reduce certain types of risk
- The different ways a portfolio can be diversified
- How index funds and ETFs can help
- The difference between diversification and asset allocation
- How to recognize over-concentration
- How rebalancing fits into a diversified investment strategy
- Common diversification mistakes to avoid
- How to build a practical diversified portfolio
The goal is not to own everything. It is to avoid relying too heavily on a single investment or source of risk.
Why Diversification Matters
Diversification matters because different investments do not always respond to the same events in the same way.
For a broader explanation of diversification and how it can reduce concentration risk, see the SEC’s Investor.gov guide to diversification.
A company can lose customers, face regulatory problems, experience a management failure, or report disappointing earnings. A particular industry can struggle because of changing technology, commodity prices, consumer demand, or government policy. A specific country or region can also experience economic or political problems.
If most of your portfolio is exposed to one company, sector, or market, one of these events can have a disproportionately large effect on your overall wealth.
Diversification reduces this concentration risk by spreading your exposure across multiple investments.
Diversification Can Reduce Investment-Specific Risk
Consider two hypothetical portfolios with $10,000 invested.
Portfolio A — Concentrated
- $10,000 in one company
If that company’s share price falls 40%, the portfolio would fall to approximately $6,000.
Portfolio B — Diversified
- $2,000 across five different investments
If one investment falls 40% while the others remain unchanged, the effect on the overall portfolio would be much smaller.
This example is simplified and does not predict how diversified investments will actually perform. In real markets, multiple investments can decline at the same time.
The important principle is that diversification can reduce the damage caused by a problem affecting one particular investment.
Diversification Does Not Eliminate Risk
Diversification is not a guarantee against losses.
During a broad market decline, stocks across many companies and industries can fall together. Economic recessions, financial crises, changes in interest rates, inflation, and other market-wide events can affect many investments at the same time.
Therefore, the goal of diversification is not:
“Make my portfolio risk-free.”
The goal is:
“Avoid allowing one investment, sector, or market to determine the outcome of my entire portfolio.”
That distinction is important.
A diversified portfolio can still lose money. It simply may have less exposure to risks that are specific to one investment or one concentrated area of the market.
Types of Investment Diversification
Diversification can be approached in several different ways. The goal is to avoid concentrating too much of your portfolio in a single source of risk.
1. Asset-Class Diversification
Asset classes can behave differently under different economic conditions.
A portfolio may include combinations of:
- Stocks
- Bonds
- Cash or cash equivalents
- Real estate investments
- Other appropriate asset classes
The right mix depends on your goals, time horizon, risk tolerance, and overall financial situation.
Asset-class diversification does not mean that one asset class will always rise when another falls. Different assets can decline at the same time, particularly during broad market stress.
2. Company or Security Diversification
Owning investments in multiple companies or securities can reduce the effect of a problem affecting one particular company.
For example, if you own shares in only one company, a major decline in that company’s value can have a large effect on your portfolio. Owning a broader group of investments can reduce the portfolio’s dependence on any single company.
Broad-market index funds and ETFs can make this easier because a single fund may hold many underlying securities.
However, investors should examine what a fund actually owns. A narrowly focused fund may contain many securities while still concentrating heavily on one industry, theme, country, or type of investment.
3. Industry or Sector Diversification
Different industries can respond differently to changes in consumer demand, economic conditions, technology, regulation, and commodity prices.
For example, a portfolio concentrated almost entirely in technology companies may be more vulnerable to events affecting the technology sector.
Holding investments across multiple sectors can reduce dependence on the performance of one industry.
4. Geographic Diversification
Investing across different countries and regions can reduce dependence on the economic conditions of a single market.
International investments can provide exposure to companies and economies outside the United States, but they also introduce additional considerations such as currency movements, political conditions, regulatory differences, and country-specific risks.
Geographic diversification therefore adds another potential source of diversification, but it does not eliminate risk.
What About Investing Over Time?
Investing a fixed amount at regular intervals is commonly called dollar-cost averaging. It can be a useful approach for managing how you enter the market, but it is not itself a form of portfolio diversification.
Diversification answers the question:
“What am I invested in?”
Dollar-cost averaging addresses:
“When and how am I investing my available money?”
Keeping those concepts separate makes it easier to understand what each strategy is designed to accomplish.
How Diversified Is Diversified Enough?
There is no single number of investments that makes a portfolio “diversified.”
Owning 20 investments does not necessarily make a portfolio safer than owning 10. What matters is how those investments are exposed to the same underlying risks.
For example, an investor might own 15 technology stocks. Although that sounds like a diversified portfolio because it contains many companies, the portfolio could still be highly concentrated in one sector.
On the other hand, a broad-market index fund may provide exposure to hundreds or thousands of companies across multiple industries through a single investment.
Look Beyond the Number of Investments
When evaluating diversification, consider:
- How much of the portfolio is invested in any one company?
- How much is concentrated in one industry or sector?
- How much depends on one country or geographic market?
- How much is invested in one asset class?
- Do several investments hold many of the same underlying companies?
- Could one economic event affect a large portion of the portfolio?
These questions can reveal concentration that is not obvious from simply counting the number of holdings.
Avoid Unnecessary Complexity
More investments do not automatically mean better diversification.
Adding several funds that own many of the same companies can create unnecessary overlap. Holding too many individual securities can also make a portfolio more difficult to monitor and rebalance.
For many investors, a small number of broad, appropriately selected investments may provide substantial diversification without creating unnecessary complexity.
The objective is not to maximize the number of holdings.
The objective is to create a portfolio where no single investment, sector, asset class, or geographic market has an unnecessarily large influence on the overall outcome.
Diversification vs. Asset Allocation: What Is the Difference?
Diversification and asset allocation are related, but they solve different portfolio problems.
Asset allocation determines how your portfolio is divided among different asset classes.
The SEC’s Investor.gov guide to asset allocation and diversification explains how asset allocation, diversification, time horizon, and risk tolerance are related.
For example, an investor might decide that a portfolio should contain:
- 70% stocks
- 25% bonds
- 5% cash
That is an asset-allocation decision.
Diversification determines how exposure is spread within those categories.
For example, the 70% stock allocation could be spread across companies, sectors, and geographic markets rather than being concentrated in a single company or industry.
A Simple Example
Imagine two investors both have a portfolio that is 70% stocks and 30% bonds.
Investor A:
- 70% concentrated in a small group of technology stocks
- 30% in bonds
Investor B:
- 70% spread across a broad range of companies and sectors
- 30% spread across appropriate bond investments
Both investors have the same broad asset allocation, but their diversification may be very different.
Investor A may have substantially more concentration risk because a large portion of the portfolio depends on one sector.
Why Both Matter
Asset allocation helps determine the portfolio’s overall exposure to different asset classes and therefore plays an important role in matching a portfolio with an investor’s time horizon and risk tolerance.
Diversification helps spread exposure within and across those investments.
A useful way to think about the relationship is:
Asset allocation = how much you own of each major asset class.
Diversification = how broadly that exposure is spread.
A well-constructed portfolio considers both rather than relying on either concept alone.
How Index Funds and ETFs Can Help With Diversification
Index funds and exchange-traded funds (ETFs) can make diversification easier because many of them hold a broad collection of securities inside a single investment.
For example, a broad-market fund may provide exposure to companies across multiple industries instead of requiring an investor to select and manage each company individually.
This can reduce the risk associated with relying on a small number of individual companies.
Broad Funds vs. Narrow Funds
Not every index fund or ETF provides the same level of diversification.
A broad-market fund may hold companies across many sectors and industries, while a sector-specific ETF may focus primarily on one part of the market.
For example:
- A broad U.S. stock-market fund may provide exposure to many companies and industries.
- A technology-sector ETF may concentrate primarily on technology companies.
- A fund focused on one country may provide geographic exposure but still carry significant country-specific risk.
- A bond fund may diversify across multiple bonds while still being exposed to interest-rate and credit risks.
Therefore, the number of holdings alone is not enough to determine whether a fund is well diversified.
Check What a Fund Actually Owns
Before using a fund for diversification, look beyond its name.
Review information such as:
- Number of holdings
- Largest holdings
- Sector exposure
- Geographic exposure
- Asset class
- Investment objective
- Expense ratio
- Degree of overlap with other investments you already own
Two different funds can hold many of the same companies. Buying both does not necessarily provide as much additional diversification as you might expect.
Diversification Does Not Mean Owning More Funds
An investor does not need to keep adding funds simply to increase the number of investments.
A few broad investments may provide substantial diversification, while a large collection of narrowly focused funds can create overlap and unnecessary complexity.
The important question is not:
“How many funds do I own?”
It is:
“What risks and investments do those funds actually expose me to?”
Understanding the underlying holdings can help you avoid accidental concentration while keeping your portfolio manageable.
Concentrated vs. Diversified Portfolio: A Practical Example
Consider two hypothetical investors, each with a $20,000 portfolio.
Portfolio A — Highly Concentrated
Suppose the portfolio is invested as follows:
- $12,000 in one technology company
- $5,000 in two other technology companies
- $3,000 in a technology-focused ETF
Although the investor owns several securities, most of the portfolio is exposed to the same sector.
If the technology sector experiences a major decline, a large portion of the portfolio could be affected at the same time.
Portfolio B — More Broadly Diversified
Now consider a different $20,000 portfolio:
- $10,000 in a broad U.S. stock-market fund
- $4,000 in an international stock-market fund
- $4,000 in a diversified bond fund
- $2,000 in cash or cash equivalents
This portfolio still carries market risk and can lose value. However, its performance is not dependent on one company or one sector to the same extent as Portfolio A.
What This Example Shows
The second portfolio is not automatically “better.” The appropriate portfolio depends on the investor’s goals, time horizon, risk tolerance, and financial circumstances.
The example illustrates a different principle:
Concentration means that a relatively small number of investments or risks can have a large effect on the overall portfolio.
Diversification spreads that exposure so that the outcome is less dependent on any single investment or source of risk.
Diversification therefore should be evaluated based on the underlying exposures, not simply the number of securities an investor owns.
How Rebalancing Helps Maintain Diversification
A diversified portfolio can gradually become less diversified or more concentrated as different investments change in value.
For example, suppose an investor starts with:
- 60% stocks
- 30% bonds
- 10% cash
If stocks rise substantially while bonds and cash remain relatively stable, stocks may eventually represent a much larger percentage of the portfolio.
The investor’s actual asset allocation would then be different from the original plan.
What Is Rebalancing?
Rebalancing means adjusting a portfolio back toward its intended asset allocation.
An investor might do this by:
- Directing new contributions toward underweighted investments
- Selling some holdings that have become overweighted
- Buying investments that have fallen below their intended allocation
- Using a combination of these approaches
The appropriate method can depend on taxes, transaction costs, account type, and the investor’s circumstances.
For more information, see the SEC’s Investor.gov explanation of portfolio rebalancing.
How Often Should You Rebalance?
There is no universal schedule that works for every investor.
Some investors review their allocation on a regular calendar schedule, while others review it when an asset class moves significantly away from a predetermined target.
The important point is to have a defined approach rather than making frequent changes based on short-term market movements.
Rebalancing is also not the same as trying to predict which investment will perform best next.
Its purpose is to bring the portfolio back toward the risk and allocation framework the investor originally intended.
Rebalancing Example
Suppose an investor targets:
- 70% stocks
- 30% bonds
After a period of strong stock-market performance, the portfolio becomes:
- 80% stocks
- 20% bonds
The investor may decide to rebalance toward the original 70/30 allocation.
This does not guarantee better returns. Instead, it helps prevent the portfolio from gradually taking on more risk than the investor originally intended.
Before selling investments in a taxable account, investors should also consider potential tax consequences.
Common Diversification Mistakes to Avoid
Diversification is straightforward in principle, but investors can still make mistakes when applying it.
1. Thinking More Investments Always Mean More Diversification
Owning many investments does not automatically create a diversified portfolio.
If most of those investments have similar characteristics or respond to the same market conditions, the portfolio may still be highly concentrated.
Focus on the underlying exposures rather than simply counting holdings.
2. Owning Several Funds With Significant Overlap
Two or more funds may appear different but hold many of the same companies.
For example, an investor could own multiple U.S. stock funds that have substantial exposure to the same large companies.
Before adding another fund, check its holdings and sector exposure to determine whether it actually adds meaningful diversification.
3. Becoming Too Concentrated in Your Employer’s Stock
Employees who receive company stock through compensation plans may unintentionally accumulate a large exposure to the same company that provides their employment income.
If the company experiences financial problems, the investor could potentially face both investment losses and employment-related financial pressure at the same time.
Reviewing employer-stock exposure as part of the overall financial picture can help identify this concentration risk.
4. Assuming International Investments Eliminate U.S. Market Risk
Adding international investments can provide geographic diversification, but international markets can also decline during global economic shocks.
International investing introduces additional risks, including currency, political, regulatory, and country-specific risks.
Geographic diversification reduces dependence on one market; it does not eliminate market risk.
5. Confusing Diversification With Safety
Diversification can reduce certain types of risk, but it cannot guarantee that a portfolio will make money.
A diversified portfolio of stocks can still experience substantial losses during a broad market decline.
Diversification should therefore be viewed as a risk-management strategy, not a guarantee of positive returns.
6. Constantly Changing Investments
Investors sometimes react to short-term market movements by continually buying and selling investments.
Frequent changes can make it difficult to maintain a consistent investment strategy and may increase transaction costs or tax consequences in taxable accounts.
A diversification strategy works best when it is based on a clear long-term plan rather than short-term market predictions.
7. Ignoring Your Overall Financial Picture
Diversification should not be evaluated only inside one brokerage account.
An investor may have investments in several accounts, retirement plans, employer stock, and other assets.
Looking at the overall portfolio can provide a more accurate picture of concentration and diversification.
The goal is to understand your total exposure and avoid taking risks you did not intentionally choose.
The Psychology Behind Diversification
Diversification is not only a portfolio-construction decision. It is also a behavioral challenge.
Investors can become concentrated because certain investments have performed exceptionally well, received significant media attention, or become familiar through their work or social circles.
Performance Chasing
When an investment has produced strong returns recently, it can be tempting to increase your exposure because you expect the trend to continue.
However, past performance does not guarantee future results.
A portfolio that becomes heavily concentrated in an asset simply because it has performed well can take on more risk than the investor originally intended.
Fear During Market Declines
The opposite problem can occur when markets fall.
An investor may sell diversified investments after a decline and move heavily into cash because the portfolio feels too risky.
This can turn a temporary market decline into a permanent loss if the investments are sold and the investor does not participate in a subsequent recovery.
Familiarity Bias
People often prefer investments they understand or encounter frequently.
For example, an employee may feel more comfortable investing heavily in the company they work for because they know the business.
Familiarity, however, does not necessarily mean lower investment risk.
A Better Approach
Instead of making portfolio decisions based primarily on which investment is currently popular or performing well, investors can establish diversification guidelines in advance.
These guidelines might address:
- Maximum exposure to an individual company
- Target exposure to major asset classes
- Target sector or geographic exposure
- When portfolio reviews should occur
- When rebalancing should be considered
- How new contributions will be allocated
A predefined framework can make it easier to avoid emotional decisions when markets become volatile.
Diversification cannot remove uncertainty from investing. It can, however, help investors avoid making their financial future unnecessarily dependent on a small number of outcomes.
A Practical Diversification Checklist
Before considering your portfolio sufficiently diversified, walk through the following questions:
Company Exposure
- Is too much of my portfolio invested in one company?
- Do I hold individual stocks that overlap significantly with my funds?
Sector Exposure
- Is my portfolio heavily dependent on one industry or sector?
- Would a major problem in that sector significantly affect my overall portfolio?
Asset-Class Exposure
- Is my portfolio invested appropriately across the asset classes I have chosen?
- Does my asset allocation match my time horizon and tolerance for investment losses?
Geographic Exposure
- Am I relying almost entirely on one country’s economy or market?
- Would geographic diversification be appropriate for my investment strategy?
Fund Overlap
- Do multiple funds contain many of the same companies?
- Have I checked the largest holdings and sector allocations of my funds?
Risk and Rebalancing
- Has market performance changed my intended asset allocation?
- Do I have a reasonable process for reviewing and rebalancing my portfolio?
Overall Financial Picture
- Have I considered investments held in all of my accounts?
- Do I have significant employer-stock exposure?
- Am I taking a level of investment risk that I intentionally chose?
You do not need to eliminate every source of risk.
The objective is to understand where your portfolio is concentrated and make deliberate decisions about the risks you are willing to accept.
Frequently Asked Questions About Diversification
Is diversification a way to avoid losing money?
No. Diversification cannot eliminate investment losses.
A diversified portfolio can still decline when broad markets fall or when multiple asset classes decline at the same time. Diversification is primarily intended to reduce the impact of risks associated with individual companies, sectors, asset classes, or geographic markets.
How many stocks do I need to be diversified?
There is no universal number.
The level of diversification depends on how the investments are distributed across companies, sectors, asset classes, and geographic markets. A single broad-market fund may provide more diversification than a portfolio containing many narrowly focused individual stocks.
Are index funds automatically diversified?
No.
Some index funds are broadly diversified, while others track a specific sector, industry, country, or market segment.
Check the fund’s holdings, investment objective, sector exposure, and geographic exposure before assuming that it provides broad diversification.
Is diversification better than investing in one stock?
Diversification can reduce the risk associated with relying heavily on one company.
However, whether an investor should own individual stocks, diversified funds, or a combination depends on their investment strategy, knowledge, risk tolerance, time horizon, and financial goals.
Does diversification reduce returns?
Not necessarily.
Diversification can reduce exposure to investments that perform exceptionally well, but it can also reduce the damage caused by investments that perform poorly.
The purpose of diversification is not to maximize the return of the single best-performing investment. Its purpose is to create a portfolio with an appropriate balance between potential return and risk.
Should I diversify internationally?
International diversification can reduce dependence on a single country’s economy and financial markets.
However, international investments also involve additional risks, such as currency fluctuations, political conditions, regulatory differences, and country-specific economic risks.
Whether international exposure is appropriate depends on the investor’s overall portfolio and objectives.
How often should I review my diversification?
There is no single review schedule that is appropriate for everyone.
Many investors review their portfolio periodically or when their actual allocation moves significantly away from their intended targets.
The goal should be to maintain a consistent investment strategy rather than constantly changing investments in response to short-term market movements.
Can diversification protect my portfolio during a recession?
No guarantee exists.
During a recession or other broad market shock, many investments can decline simultaneously. Diversification may reduce exposure to some investment-specific risks, but it cannot prevent losses caused by widespread market declines.
Related Reading
Index Funds vs ETFs: Which Is Better for Long-Term Investors?
Investment vs Savings: How to Grow Your Money Smarter
How Much Should You Save vs Invest?
Emergency Savings or Investment Portfolio: What Comes First?
How to Invest Safely: 10 Smart Strategies
Conclusion
Diversification is one of the fundamental principles of portfolio risk management.
Its purpose is not to eliminate investment risk or guarantee positive returns. Instead, diversification can reduce the effect that a single company, sector, asset class, or geographic market has on the overall portfolio.
A practical diversification strategy considers:
- Different asset classes
- Multiple companies or securities
- Different industries and sectors
- Geographic exposure
- Fund holdings and overlap
- Appropriate asset allocation
- Periodic portfolio review and rebalancing
The right level of diversification depends on your financial goals, time horizon, risk tolerance, and overall financial situation.
The objective is not to own as many investments as possible.
The objective is to understand your exposures, avoid unnecessary concentration, and take only the risks you intentionally choose.
Before making investment decisions, consider your individual circumstances and, when appropriate, consult a qualified financial professional.
Disclaimer
This article is for educational and informational purposes only and is not financial, investment, tax, or legal advice. Investment values can rise or fall, and diversification cannot eliminate all investment risk. Consider your individual circumstances and consult a qualified professional when appropriate.