Jane Street's $662B Filing: When 15% of Your AUM Is in SPY

The Number

Jane Street Group filed Q4 2025 with $662.12B across 17,120 positions. SPY alone: $95.9B (15.4%).

What This Tells You About Market Makers

Jane Street is a quantitative trading firm. Their 13F reflects:

• ETF arbitrage positions (SPY, IWM, commodity ETFs)
• Delta hedging against options books
• Market-making inventory across thousands of securities

AUM: $662.12B
Positions: 17,120
Top-5 concentration: 37.8%
ETF + commodity: ~$145B
SPY alone: $95.9B (15.4%)

The Doubling

Jane Street's AUM has more than doubled recently. This reflects both market appreciation and increased market-making activity.

For Quant Researchers

When filtering 13F data for investment signals, exclude or separately analyze market makers like Jane Street, Citadel, and Susquehanna. Their position changes reflect inventory management, not investment views.

Full analysis: https://13finsight.com/research/jane-street-q4-2025-662b-spy-15-percent-portfolio?utm_source=devto&utm_medium=social&utm_campaign=article_ops_0318

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Originally published at 13finsight.com