By Steve Giles
For most investors, market volatility doesn’t just create financial stress — it creates emotional stress. When markets fall sharply, even disciplined investors can start asking difficult questions.
“Am I taking too much risk?”
“Should I make a change?”
“Can my retirement plan withstand this?”
At Landaas & Company, we believe diversification is about more than portfolio construction. It is about helping clients build confidence.
- Confidence to stay invested during difficult markets
- Confidence to avoid emotional decisions
- Confidence that their portfolio is built not just for today’s environment, but for the uncertainties of tomorrow
That is where diversification matters most. At its best, diversification does more than improve portfolio construction — it helps investors remain disciplined when emotions are running highest.
What does diversification really mean when investing in the stock market?
Diversification is one of the most widely used — and often misunderstood — concepts in investing.
Many investors believe diversification simply means owning many different stocks. But owning 50 stocks in the same sector or all large-cap U.S. growth companies may provide less diversification than owning a smaller number of assets that behave differently under changing market conditions.
At its core, diversification is not about quantity. It is about correlation.
True diversification means combining investments whose returns do not move in lockstep. It means building a portfolio of assets that behave differently, so you can improve expected returns relative to risk. When done effectively, diversification can reduce portfolio volatility while preserving — or even improving — long-term expected returns.
Diversification is about risk management, not maximizing returns
One common misconception is that diversification is designed to maximize returns.
Its primary purpose is different.
Diversification acknowledges a simple reality: None of us can predict the future with certainty. Markets change, leadership rotates and surprises happen. A well-diversified portfolio helps ensure that one wrong call does not derail an entire financial plan. While a concentrated portfolio may outperform dramatically when conditions are favorable, that concentration also increases the risk of significant underperformance when markets shift.
Diversification accepts a trade-off: You may sacrifice some upside in the best-case scenario in exchange for greater resilience across a wider range of outcomes.
For many investors, the goal is not simply to maximize returns in the best years. It is to build a portfolio strong enough to weather difficult years without abandoning the long-term plan. That matters because the biggest threat to investment success is often not market volatility — it is investor behavior during volatility.
The foundation: Harry Markowitz and modern portfolio theory
The modern understanding of diversification began with economist Harry Markowitz in the 1950s. Markowitz introduced what became known as modern portfolio theory (MPT), demonstrating mathematically that investors should evaluate investments not only by their expected returns, but also by how they interact with one another inside a portfolio.
His key insight was revolutionary: A portfolio should be judged as a whole — not by evaluating each investment independently. This work earned Markowitz the Nobel Memorial Prize in Economic Sciences in 1990.
Before his research, investors largely focused on selecting “good” individual securities.
The real question became: How do different investments behave together?
The efficient frontier
Markowitz’s work introduced another important concept: the efficient frontier.
The efficient frontier is simply a framework for building portfolios that aim to maximize return without taking unnecessary risk.
Think of it this way:
- Some portfolios take too much risk for the return they offer.
- Some portfolios are inefficient because better combinations exist.
- The best portfolios lie on the efficient frontier.
Put simply, the goal is to build a portfolio that seeks the most return possible without taking unnecessary risk.
By combining assets with different risk and return characteristics — such as U.S. equities, international equities, fixed income, real assets and cash — investors can often create portfolios that are more efficient than portfolios concentrated in a single asset class.
In simple terms: Good diversification can improve the risk/return trade-off.
Asset allocation: The biggest driver of portfolio behavior
This leads to one of the most important decisions an investor makes: asset allocation.
Asset allocation refers to how a portfolio is divided among major asset classes, including:
- Stocks
- Bonds
- Cash
- Real estate
- Alternative investments
Many investors spend enormous energy trying to pick the perfect stock. But research suggests that portfolio outcomes are driven far more by asset allocation than by individual security selection.
One of the most cited studies in investment management came in 1986 from Gary P. Brinson, L. Randolph Hood and Gilbert L. Beebower.
Their landmark research examined pension fund performance and found that the overwhelming majority of portfolio return variability over time was explained by asset allocation decisions — not market timing or security selection.
The takeaway was profound: How you allocate your assets matters more than which individual investments you own.
This does not mean stock selection has no value; rather, it means the broader architecture of the portfolio often matters more.
What diversification looks like in practice
A properly diversified portfolio considers exposure across multiple dimensions:
Asset class diversification — balancing stocks, bonds, cash and alternatives
Geographic diversification — investing across U.S. and international markets
Sector diversification — avoiding concentration in one industry such as technology, healthcare or financials
Style diversification — balancing growth, value, and large-cap and small-cap exposure
Each respective layer reduces dependence on any single economic outcome, which matters because markets are unpredictable.
Final thoughts
Successful investing is not about predicting the future perfectly. It is about preparing thoughtfully for whatever the future may bring. It is about building resilient portfolios.
Because in retirement, peace of mind matters just as much as performance.
At Landaas & Company, we believe diversification is one of the most important tools for helping investors preserve confidence during uncertain times. And because diversification helps investors stay invested during volatility, they are less likely to make a change based upon emotions like fear or greed when making investment decisions.
Steven Giles is a Senior Vice President at Landaas & Company LLC