Think Your Mutual Funds Are Diversified? Portfolio Overlap Could Be Undermining Your Returns

What Portfolio Overlap Means for Mutual Fund Investors

If you hold several mutual funds, you may assume you’re well-diversified and better protected against risk. But if those funds own many of the same stocks, you’re exposed to something called portfolio overlap. Understanding and measuring this overlap is essential for true diversification in your investments.

How Portfolio Overlap Happens—and Why It Matters

Many Indian mutual funds, especially within similar categories (like large-cap equity), track the same benchmarks or compete within a limited pool of blue-chip stocks. This naturally leads to overlap, where two or more funds hold many of the same companies.

For example, if Fund A and Fund B both track the Nifty 50, their top 10 or 15 holdings may be almost identical. As a result, your portfolio’s exposure to these stocks is effectively multiplied.

The Risks of High Overlap

1. Diversification illusion: Holding multiple funds doesn’t reduce risk if they’re invested in the same companies.
2. Compounded losses: If a commonly-held stock underperforms, you feel the pain across several funds, not just one.
3. Higher costs: You may pay multiple funds’ expense ratios without gaining additional diversification benefit.

How to Measure Portfolio Overlap

You don’t need fancy tools to get a basic sense of overlap. Most Indian mutual fund websites and factsheets disclose their top holdings and their weightage in the fund. Here’s how to check:

1. List the Top Holdings: Write down the top 10-15 holdings of each fund you own.
2. Compare Holdings: Check how many stocks appear in multiple funds. Note both the number and the weight each stock carries.
3. Calculate Percentage Overlap: Divide the number of overlapping stocks by the total holdings (commonly within the top 10 or 20 holdings) to get a rough percentage.

Example: Measuring Overlap

| Holding | Fund A (Weight) | Fund B (Weight) | Overlap

|---------------|----------------|----------------|---------

| Reliance | 9% | 8% | Yes

| HDFC Bank | 7% | 6% | Yes

| Infosys | 6% | 7% | Yes

| ITC | 5% | 0 | No

| Tata Motors | 0 | 4% | No

In this example, three out of five stocks are common, signaling 60% overlap among the top holdings.

When Does Overlap Become a Problem?

• Up to 35% overlap: Common and usually not worrisome among funds within the same category.
• Above 50% overlap: Time to reassess—diversification benefit drops sharply.
• Above 70% overlap: Funds are almost mirror images; additional funds add very little value.

What Should Investors Do?

• Don’t chase more funds for the sake of it: More doesn’t mean better if the underlying stocks are the same.
• Check overlap before adding a fund: Especially if it’s in the same or similar category as your existing funds.
• Aim for meaningful diversification: Some overlap is inevitable. The key is to balance sector, style, and market cap to avoid concentration.

Is All Overlap Bad?

Not necessarily. Funds that follow the same benchmark are bound to have some overlap. But excessive duplication, especially where total expenses add up, often does more harm than good.

The bottom line: True diversification comes not just from the number of funds, but from the uniqueness of their holdings.