S&P 500 Market Cap Concentration 2026 — Westmount Research
Index Weight Distribution
How much of the S&P 500 is controlled by the top stocks?
Key Findings
What the concentration data reveals
Top 20 Stocks by Index Weight
Sector Concentration
Weight of each GICS sector in the S&P 500
All S&P 500 Companies by Weight
Click any column to sort · Search by ticker or company name
#
Ticker
Company
Sector
Weight %
Mkt Cap ($B)
P/E
Frequently Asked Questions
Common questions about S&P 500 concentration
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?" westmountfundamentals.com/market-concentration. Published March 9, 2026.