Portfolio Overlap: The Hidden Risk in ‘Diversified’ DIY Portfolios

Mutual fund portfolio overlap is one of the most common and most overlooked risks in DIY investing. At first glance, many DIY investor portfolios appear well-diversified.

• 4–5 mutual funds

• A mix of large-cap, flexi-cap, and mid-cap strategies

• A few direct stocks

On paper, this looks like a balanced, diversified allocation.

But beneath the surface, many such portfolios suffer from a hidden and often overlooked risk: portfolio overlap.

What is Portfolio Overlap?

Portfolio overlap occurs when multiple funds or investments in your portfolio hold the same underlying securities.

For example:

• You own two different mutual funds

• Both funds have significant exposure to the same large-cap stocks

• Your actual exposure to those stocks becomes much higher than intended

• If you also hold large cap stocks in your direct equity portfolio – it adds to the concentration.

So while you think you are diversified across funds, you are concentrated at the stock level.

Few examples below, which show ~40% overlap between certain Flexi Cap and Large Cap funds

Source: Creso

Why Is Portfolio Overlap So Common?

Portfolio overlap is especially common in DIY portfolios for a few reasons:

Popular Funds Own Popular Stocks

Most actively managed funds gravitate toward market leaders, high-quality large-cap names and sector leaders. So multiple funds end up holding the same stocks.

Style Overlap Across Categories

In theory, categories differ – Large Cap, Flexi Cap, Multi Cap. In practice, many portfolios converge toward the same large-cap heavy structure. Because fund managers are benchmark-aware and liquidity constraints push capital into the same names.

Performance-chasing Behaviour

Typical behaviour:

• Fund A performs well → investor buys

• Fund B performs well → investor adds

• Fund C shows up in rankings → investor adds again

But what’s missed - These funds often own the same core holdings.

Lack of Portfolio-Level View

Most investors track fund returns and individual holdings. But not combined exposure across the entire portfolio.

Why Portfolio Overlap is a Problem?

At first glance, overlap may not seem harmful. After all, you are still invested in “good companies”. But the risks are real.

Illusion of Diversification

You may believe - “I have 8 funds, so I am diversified.” But in reality, your top 10 stocks may form 50–60% of your portfolio indirectly. This creates hidden concentration risk.

Amplified Downside Risk

If a heavily owned stock or sector corrects - multiple funds fall simultaneously and portfolio drawdown is sharper than expected.

Lower Risk-Adjusted Returns

Owning similar funds leads to return duplication - with no incremental diversification benefit. So portfolio risk metrics like standard deviation stay high. You also bear higher cost (expense ratio) without added value.

So your overall risk-adjusted return (measure using sharpe ratio and other metrics) drops.

Missed Opportunities

By repeatedly allocating to similar exposures, you may miss different sectors, different market caps and alternative strategies.

How to Identify Portfolio Overlap?

You can either manually compare top 10 holdings of each fund and identify common names. Or you can use one of the several platforms that provide overlap comparison or overlap %.

When assessing overlap, you should also assess sector overlap – even though stocks may not overlap, you may be overexposed to a particular sector.

Identifying portfolio overlap is about asking yourself a simple question - “If all my funds were merged, what would my portfolio look like?”

How to Reduce Overlap?

Reducing overlap doesn’t mean owning more funds — often, it means owning fewer.

Fewer Funds, More Thought

Most investors don’t need 10–12 funds. A well-constructed portfolio can often work with 4–6 complementary funds.

Choose Complementary Strategies

Instead of similar funds, combine:

• Large-cap / index /Flexi-cap

• Mid/small-cap / Focused

• Multi-Asset/Hybrid

• International / thematic (if suitable)

Avoid Performance Chasing

Before adding a new fund check how different it really is from what you already own.

Periodic Portfolio Review

At least once a year, review overlaps and rebalance if needed.

‘Index Hugging’: When Your Active Fund Acts Like a Passive One

A number of portfolios today (mainly large-cap and flexi-cap funds) are very index-aware – that is, their portfolio closely replicates the benchmark index they are tracking. Since majority of their portfolio replicates the index, the ‘alpha’ (excess return over the benchmark index) generated maybe limited.

An example of overlap of a large cap fund with the Nifty 50 Index

Source: Creso

If your funds closely mirror benchmark weights and hold similar top stocks, then you are effectively paying ‘active’ fees for index-like returns. You can prefer passive index funds instead, where costs are lower.

Overlap is Not Always Bad

Some level of overlap is natural and even desirable. Because:

• Quality companies will appear across portfolios

• Avoiding overlap completely may reduce quality exposure

The goal is: Manage overlap, not eliminate it entirely.

Key Takeaways: Managing Mutual Fund Portfolio Overlap

DIY portfolios often look diversified on the surface but may be concentrated beneath the hood. Portfolio overlap is a subtle risk - easy to ignore in rising markets, but more visible during corrections.

A disciplined, structured approach that focuses on portfolio-level construction rather than individual fund selection can help build more resilient portfolios.

If you are looking to review your portfolio for hidden risks or build a more structured investment strategy, we would be happy to connect.