Portfolio Overlap Explained: How Indian Investors Can Measure Hidden Duplication

Portfolio Overlap at a Glance

Why Overlap Develops

Bull Run's Three-Layer Overlap Map

Step 1: Collect Current Holdings Data

Use the most recent available portfolio disclosure for every mutual fund and ETF. SEBI's current mutual-fund disclosure framework requires scheme portfolios to be disclosed monthly, and AMFI provides a central portfolio-disclosure facility. Monthly fund factsheets are also a practical starting point.

Collect:

• scheme name and plan;
• portfolio disclosure date;
• security name and ISIN;
• weight in scheme assets;
• cash and derivative exposure;
• sector and market-cap classification;
• benchmark;
• expense ratio and exit load;
• fund manager and mandate;
• investor's current value in the scheme.

Use ISIN where possible because company names can vary across files. Compare disclosures from the same month to avoid creating false differences from timing.

Direct and Regular Plans of the Same Scheme

AMFI explains that direct and regular plans of the same mutual-fund scheme generally have the same underlying portfolio and fund manager while differing in expense structure. Owning both plans does not create meaningful security diversification.

The investor should treat them as one economic holding for overlap analysis:

The choice between plans is an implementation and advice decision—not an overlap solution.

Step 2: Calculate Stock-Count Overlap

The simplest overlap metric is the Jaccard ratio:

If Fund A holds 20 stocks, Fund B holds 25 and 5 are common:

This metric is useful for identifying repeated names but ignores weights. A common 0.2% holding and a common 10% holding count equally.

Step 3: Calculate Weighted Common-Holdings Overlap

A more useful pairwise measure adds the lower weight of every common holding:

Identical portfolios have 100% weighted overlap. Portfolios with no common securities have 0% exact-stock overlap.

The two funds share 19% of portfolio weight exactly. They may still have much higher sector or factor overlap.

Step 4: Calculate Investor-Level Look-Through Exposure

Pairwise fund overlap does not show the investor's actual concentration. Multiply each underlying weight by the fund's share of the investor's equity portfolio.

Then add all routes:

Example:

• Fund A is 50% of equity and holds Company X at 8%: contribution 4%.
• Fund B is 30% of equity and holds Company X at 6%: contribution 1.8%.
• Company X is held directly at 5%.

The demat account shows 5%. The economic portfolio owns 10.8%.

Look-Through Exposure Is the Most Important Number

Step 5: Calculate Combined Effective Holdings

Once look-through stock weights are calculated across the full portfolio, use HHI:

An investor may hold four funds with 150 total line items, but repeated large holdings can produce a much smaller effective count.

This calculation requires normalising the complete combined portfolio to 100%, including residual cash or non-equity exposure if it is part of the analysed sleeve.

Fund Count vs Effective Holdings

Step 6: Measure Sector Overlap

Calculate each fund's contribution to the investor's sector exposure:

Then add direct-stock sectors.

Example:

• Index fund contributes 14% financial-services exposure to total equity.
• Flexi-cap fund contributes 6%.
• Direct banks and NBFCs contribute 9%.

The portfolio may contain several products and companies while remaining dependent on one sector.

Sector Similarity Without Exact Stock Overlap

Fund A may hold Bank A and Insurer A. Fund B may hold Bank B and NBFC B. Exact stock overlap can be low while both remain sensitive to credit conditions, rates and regulation.

Compare:

• sector weights;
• sub-sector weights;
• cyclical versus defensive exposure;
• capital intensity;
• domestic versus export demand;
• state-owned versus private companies;
• commodity winners and losers.

Step 7: Measure Economic Risk-Cluster Overlap

Economic overlap often matters more than exact overlap during a market stress event.

Step 8: Measure Market-Cap Overlap

Different product labels can concentrate in the same market-cap segment.

Review large-, mid- and small-cap exposure using current classifications. A flexi-cap fund may already hold meaningful mid-cap exposure. Adding a mid-cap fund and direct mid-cap stocks can create a much larger active tilt than intended.

Step 9: Measure Factor Overlap

Funds and stocks can share investment characteristics even when holdings differ:

• quality and profitability;
• value and cyclical earnings;
• momentum;
• low volatility;
• high dividend yield;
• small size;
• high growth and high valuation;
• state ownership;
• high leverage.

A quality index, flexi-cap fund and direct portfolio of branded compounders may all depend on premium valuations remaining supported. Exact overlap can be moderate while factor overlap is extreme.

Factor Overlap Audit

Step 10: Measure Portfolio-Role Overlap

Every product should have one sentence describing its job.

Possible jobs include:

• broad Indian equity core;
• mid-cap selection;
• small-cap diversification;
• international diversification;
• value or momentum factor exposure;
• direct high-conviction stocks;
• temporary sector or special-situation allocation.

When two products have the same sentence, compare whether both are needed.

Bull Run's Overlap Utility Test

This is a conceptual test. It classifies overlapping products as useful or wasteful.

How Much Overlap Is Too Much?

There is no universal threshold. Use pairwise weighted overlap as a diagnostic:

These ranges are analytical guides, not regulatory limits. A 40% overlap can be acceptable in a core-plus-active structure when the non-overlapping 60% performs a valuable role. A 15% overlap can still be wasteful when the remaining holdings carry the same factors and sectors.

Overlap and Fees

Overlapping products can charge different fees for similar exposure.

Then calculate the cost of the overlapping route:

The relevant question is whether the distinct part of the product and the manager or implementation benefit justify the recurring cost.

A fund does not become redundant merely because some holdings overlap with an index. Active managers often begin from the same investable market. The question is whether differences in weights, non-index holdings, downside management and process are sufficiently valuable.

Overlap and Manager Risk

Two funds from different AMCs may hold similar stocks but rely on independent research teams and risk systems. This can create operational and manager diversification. Two schemes from one AMC may hold different securities but share the same house view, valuation philosophy and risk process.

Review:

• fund manager and supporting team;
• investment philosophy;
• benchmark and eligible universe;
• turnover and holding period;
• cash policy;
• concentration limits;
• AMC-level sector or style bias;
• changes in manager or mandate.

Manager diversification is useful only when the processes are genuinely independent.

Overlap Changes Over Time

Fund portfolios are not static. A pair with low overlap can converge; a pair with high overlap can diverge. Review:

• current monthly portfolios;
• six- or twelve-month average overlap;
• new common holdings;
• changes in active weights;
• style drift;
• cash and derivatives;
• fund-manager changes;
• scheme mergers or mandate changes.

A one-month snapshot can be distorted by temporary cash or portfolio transition. Persistent overlap matters more than one observation.

Bull Run's Overlap Persistence Score

Also record the range:

High average overlap with a narrow range indicates stable duplication. High average overlap with a wide range may reflect active portfolio rotation. This is a monitoring tool, not a prediction of returns.

Worked Example 1: Two Similar Large-Cap Funds

An investor holds 30% of equity in Fund A and 30% in Fund B. Pairwise weighted overlap is 58%, sector exposures are similar and both use the same large-cap benchmark. The non-overlapping holdings are small positions.

The second fund adds limited diversification while increasing monitoring. The investor can keep the fund with lower cost, better tracking or stronger process unless manager diversification is deliberately valued.

Worked Example 2: Index Core and Active Fund

An index fund and active fund have 42% weighted overlap. The active fund significantly underweights the index's largest sector and owns differentiated mid-cap positions.

The overlap is not automatically excessive. The common holdings provide broad market continuity while the active weights create a distinct portfolio. The investor evaluates whether the difference is persistent and worth the fee.

Worked Example 3: Direct Stocks Duplicate the Core

An investor owns 70% in a broad index core and 30% in ten direct large-cap stocks. Eight direct stocks are among the index's largest constituents.

The direct sleeve does not create diversification. It creates deliberate or accidental overweights. Each direct position must justify why the company deserves more capital than the market-weighted core already provides.

Worked Example 4: Low Exact Overlap, High Capex Risk

A railway fund and a direct industrial portfolio share only 8% exact stock overlap. However, 65% of the combined equity exposure depends on public capital expenditure, order execution and small-company liquidity.

Security overlap is low. Economic overlap is severe. The investor needs an independent return engine rather than a third capex product.

Worked Example 5: Flexi-Cap Plus Mid-Cap Fund

A flexi-cap fund already invests 28% of its assets in mid caps. It represents 50% of the investor's equity portfolio, contributing 14% mid-cap exposure. A separate mid-cap fund represents 25%, and direct mid caps add 10%.

The scheme labels do not reveal the final allocation. The investor has a mid-cap-heavy portfolio.

Worked Example 6: Direct and Regular Plans

An investor holds the direct plan and regular plan of the same scheme in different folios. Security overlap is effectively complete because the plans share the scheme portfolio.

The investor should combine them for economic analysis and separately review cost, advice and switching implications under current tax and fund rules.

Worked Example 7: Household-Level Overlap

One spouse owns an index fund, the other owns a flexi-cap fund and both hold employer shares in a bank. Each account appears diversified. Household look-through analysis shows 16% exposure to the same bank and more than 35% to financial services.

Risk should be measured at household level when goals and liabilities are shared.

Worked Example 8: International Fund Is Not Automatically Different

An Indian investor adds an international technology fund to diversify. The domestic portfolio already owns Indian IT exporters whose revenue depends on the same global clients and technology budgets.

The international fund adds geography and currency but may reinforce global technology-factor exposure. It can still be useful, but its actual role must be described accurately.

Worked Example 9: Small-Cap Fund and Direct Small Caps

A small-cap fund provides broad selection, while the direct portfolio holds six researched niche companies. Exact overlap is low, but both are exposed to small-cap liquidity and risk appetite.

The structure can be coherent when the combined small-cap allocation, sector clusters and position sizes remain within policy bands. The fund diversifies company risk but does not remove segment risk.

Worked Example 10: Legacy Funds Create Administrative Overlap

An investor has seven old funds accumulated over ten years. Four now perform the same diversified-equity role. Several have small values and require separate statements, nominees and monitoring.

Even when exact overlap is moderate, administrative complexity can exceed the diversification benefit. Consolidation can improve governance of the personal portfolio.

When Overlap Is Intentional and Useful

• A direct stock deliberately overweights a company already owned through the core.
• Two managers provide meaningfully different processes despite common market leaders.
• A tax-aware transition requires temporary duplication.
• Operational diversification across AMCs or platforms is valuable.
• A broad fund and specialist fund divide core and satellite roles.
• One product provides liquidity while another provides less liquid active exposure.
• Household accounts have separate goals and risk policies.

Intentional overlap should be documented as a total exposure, not hidden behind separate product labels.

When Overlap Is Wasteful

• Products have the same benchmark, holdings, role and similar costs.
• Direct and regular plans of the same scheme are treated as diversification.
• A new fund is added because of recent performance rather than portfolio need.
• Several active funds repeatedly own the same popular companies.
• Direct stocks duplicate fund holdings without a deliberate overweight thesis.
• Sector and factor concentration exceed the investor's limits.
• Small legacy funds remain only because selling or consolidating has been postponed.
• The investor cannot explain what unique risk or return source each product provides.

The Overlap Decision Matrix

How to Simplify an Overlapping Portfolio

1. Define the core benchmark and market-cap role.
2. Assign one sentence to every product and direct-stock sleeve.
3. Combine direct and regular holdings of the same scheme for economic analysis.
4. Calculate exact and look-through company exposure.
5. Measure sectors, factors and economic clusters.
6. Rank overlapping products on role, process, cost, liquidity and tax impact.
7. Stop new contributions to redundant products.
8. Redirect new money and distributions to the retained structure.
9. Sell or switch gradually when tax, exit load and market conditions matter.
10. Set a deadline so temporary duplication does not become permanent.

Use the Lowest-Friction Simplification Method

Verify current tax rules, exit loads and scheme documents before implementation.

The Quarterly Portfolio Overlap Audit

Portfolio Overlap Worksheet

Common Portfolio-Overlap Mistakes

1. Comparing only the top ten holdings

Important overlap can exist below the largest disclosed names.

2. Counting common stocks without weights

A repeated 10% holding matters more than a repeated 0.2% holding.

3. Ignoring direct stocks

The most familiar direct holdings often duplicate fund leaders.

4. Treating different AMCs as diversification

Independent fund houses can still own the same market consensus.

5. Treating scheme categories as independent risks

Flexi-cap, large-and-mid-cap and focused funds can share substantial exposures.

6. Ignoring factor overlap

Different stocks can depend on the same valuation or momentum regime.

7. Ignoring changing fund portfolios

One static overlap report can become outdated.

8. Consolidating solely because exact overlap is high

Manager, weighting and portfolio-role differences may still be valuable.

9. Keeping redundant funds to avoid one tax event

Tax-aware transitions need a deadline and target architecture.

10. Believing zero overlap means zero common risk

Economic clusters can connect completely different securities.

How Bull Run Features Fit Overlap Analysis

Use the Bull Run watchlist to store new ideas before adding another layer of exposure. The proposed holding should improve the combined portfolio rather than merely look attractive independently.

Use Bull Run Compare to compare direct holdings already present through funds. Review growth, margins, debt, cash flow, return ratios and valuation before deciding whether an intentional overweight is justified.

The Stock Battle tool helps when two companies compete for the same sector or risk-cluster budget. Smart Screeners can identify genuinely differentiated candidates rather than another version of an existing exposure.

Primary Official Sources

• AMFI: mutual-fund portfolio disclosure
• AMFI: monthly mutual-fund factsheets
• SEBI: mutual-fund monthly and half-yearly portfolio disclosure requirements, 2026
• SEBI Investor: understanding mutual funds
• SEBI Investor: index mutual funds and diversification
• SEBI Investor: sectoral and thematic fund concentration
• AMFI: direct and regular plans share the same scheme portfolio
• NSE Indices: Nifty 50 methodology and coverage
• NSE Indices: Nifty 500 methodology and coverage
• Bull Run data sources and coverage policy