What percentage of the S&P 500 is the top 10 stocks?

As of March 2026, the top 10 stocks represent approximately 37.3% of the S&P 500 by market cap weight. The top 5 alone account for 25.1%. This level of concentration is historically elevated.

Is the S&P 500 too concentrated?

The S&P 500's concentration is at elevated levels. The top 20 stocks control 47.6% of the index, meaning 4% of companies drive nearly half the returns. This creates risks if large-cap tech declines, as the bottom 400+ stocks only make up ~52% of the index.

Which stock has the highest weight in the S&P 500?

NVIDIA (NVDA) has the highest weight at 7.08%, followed by Apple (AAPL) at 6.19% and Microsoft (MSFT) at 4.97%. The top 3 stocks alone represent 18.2% of the index.

What is market cap weighting?

Market cap weighting means each company's influence on the index is proportional to its total market value. A $4 trillion company like NVIDIA has ~700x more influence than a $6 billion company at the bottom of the index. This is why the S&P 500 can rise even when most stocks fall.

Should I invest in equal-weight S&P 500 instead?

The Invesco S&P 500 Equal Weight ETF (RSP) gives each stock ~0.2% weight regardless of size. This reduces concentration risk and increases exposure to mid-cap stocks. Equal-weight has historically outperformed during periods when large-cap leadership rotates, but underperforms when mega-caps dominate (as in 2023-2025).

S&P 500 Market Cap Concentration 2026

All S&P 500 Companies by Weight

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#	Ticker	Company	Sector	Weight %	Mkt Cap ($B)	P/E

Methodology

This study analyzes the market capitalization concentration of the S&P 500 index as of March 2026.

Constituent weights sourced from SlickCharts.com, which derives data from the S&P Dow Jones Indices.
Financial metrics (sector, P/E ratio, market cap) enriched via Finviz screener for all 501+ constituents.
Concentration metrics computed as cumulative weight of top N stocks (top 5, 10, 20, 50).
Sector breakdown uses Finviz sector classifications (similar to GICS).
Data represents a point-in-time snapshot. Weights change daily as prices move.
Some dual-class stocks (e.g., GOOGL/GOOG) appear as separate entries per index methodology.

Cite This Research

Westmount Research. "S&P 500 Market Cap Concentration 2026: How Top-Heavy Is the Index?" westmountresearch.com/market-concentration. Published March 9, 2026.

S&P 500 Market Cap Concentration 2026

Index Weight Distribution

Key Findings

Top 20 Stocks by Index Weight

Sector Concentration

All S&P 500 Companies by Weight

Frequently Asked Questions

Methodology

Cite This Research