Market Cap vs Equal Weighted Indices | Index One

In this edition of Index One Insights by Index One, we explore the differences between market cap and equal weighted indices and which to consider for a client’s investment portfolio.

Also in this edition:

📊 POLL: What is the first thing you look for when choosing an ETF?

📈 BX Smart Alpha US Large-Cap Multi-Factor Strategy

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Market Cap vs Equal Weighted Indices | Index One

When it comes to index funds, most people are familiar with the S&P 500, but not all index funds are created equal, especially when it comes to how they’re weighted.

Two of the most common methods are market capitalization weighting and equal weighting.

This article will break down the pros and cons of market cap vs equal weighted indices, helping investors better understand the differences and make more informed portfolio decisions.

Market Cap Weighted Indices

What Are Market Cap Weighted Indices?

A market cap weighted index assigns weights to its constituents based on their market capitalization. The bigger the company, the larger its influence on the index.

Examples:

• i1 Market Cap 3000
• i1 US Mega Cap 50
• i1 US Top 7

Why Market Cap Weighted Indices?

• Reflects Real Market Dynamics: Represents the actual investment landscape more accurately.
• Passive & Scalable: Easy to track and manage; fund flows don’t distort the index.
• Lower Turnover & Costs: Changes only occur when companies are added/removed or experience significant market cap shifts.
• Proven Long-Term Performance: Historically strong due to the “momentum effect”, where top-performing companies receive greater weights and continue to influence returns as their success persists.

Cons of Market Cap Weighted Indices

• Concentration Risk: A few mega-cap stocks can dominate returns.
• Momentum Bias: Overweights overvalued stocks, underweights undervalued ones.
• Underexposure to Small/Mid Caps: Limits diversification benefits from smaller companies.

Equal Weighted Indices

What Are Equal Weighted Indices?

An equal weighted index gives each constituent the same weight, regardless of size.

Examples:

• i1 US 100 (Equal Weight)
• i1 US Financial 100 (Equal Weight)

Why Equal Weighted Indices?

• Diversification: Reduces concentration in mega-cap stocks.
• Greater Small/Mid-Cap Exposure: Taps into the performance of less dominant firms.

Cons of Equal Weighted Indices

• Higher Turnover: Requires frequent rebalancing, leading to higher trading costs and tax inefficiencies.
• Less Realistic in Scale: Difficult to replicate for large institutional portfolios.
• Volatility: Tends to be more volatile, especially during bear markets or crises.
• Tracking Error: May deviate significantly from the benchmark index.

Performance Comparison: i1 US 100 Market Cap vs Equal Weighted

Using Index One’s seamless backtesting tool, we compared the performance of the i1 US 100 Market Cap and Equally Weighted indices from 2020 onwards, with monthly rebalancing.

Here are the results.

Analysis

In 2020:

• Both indices dropped sharply.
• Equal weight fell slightly more but began recovering in sync with market cap.

Mid-2020 to End-2021:

• Both indices grew strongly.
• Market Cap Index pulled ahead due to big tech outperformance.

In 2022:

• Market-wide drawdown affected both.
• Equal weight showed slightly less volatility, buffering losses better.

In 2023–2025:

• Market Cap Index accelerated faster, significantly outperforming Equal Weight.
• Reflects dominance of mega-caps.

Market Cap vs Equal Weighted: Which One is Better?

Both index weighting strategies have their place in a diversified investment strategy. Market cap indices are efficient and practical, while equal weighted indices offer a contrarian edge (potential advantage gained by going against market trends or investor sentiment) and deeper diversification. The right choice often comes down to your clients’ risk tolerance, time horizon, and investment philosophy.

Index One’s rules-based and systematic platform makes it faster than ever to build fully customized market cap or equal weighted indices tailored to your strategy. Try it now.

POLL: What is the first thing you look for when choosing an ETF?

Choosing an ETF should be an informed and guided process.

There are many aspects to consider when choosing an ETF, including investor values and investment goals. Other metrics to look out for include benchmark constituents and tracking difference.

💡 What is the first thing you look for when choosing an ETF?

Vote now

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Index One calculates the BX Smart Alpha US Large-Cap Multi-Factor Strategy is a 48-stock equal weighted equity portfolio, designed to provide a style factor risk-neutral portfolio, using Libra’s proprietary Smart Alpha stock selection and factor risk models.

Smart Alpha’s systematic rebalancing approach ensures that both the risk profile and expected return of the portfolio are maintained in line with the strategy objectives of sustainable compound returns.

Create a custom index or enhance your current indexing workflows with Index One’s comprehensive index backtesting, maintenance, dissemination and reporting solutions.

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