U.S. spot Bitcoin ETFs shattered 2025 trading records last week, with BlackRock’s iShares Bitcoin Trust (IBIT) leading the charge through its 30th consecutive day of inflows. The surge comes as institutional investors capitalize on arbitrage opportunities and renewed confidence in Bitcoin’s $100,000+ price floor.
Daily trading volumes across all spot Bitcoin ETFs surpassed $4.5 billion on May 23 alone, according to data from SoSoValue. This capped a week that saw cumulative inflows reach $1.5 billion across just two days (May 21-22), putting May 2025 on track to break November 2024’s $6.49 billion monthly record.
The basis trade strategy—simultaneously holding spot ETF shares and shorting CME Bitcoin futures—has become particularly lucrative, with annualized yields nearing 9%. This helped drive CME futures volumes to $8.4 billion (80,000 BTC) on May 20, the highest since April 23.
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BlackRock’s iShares Bitcoin Trust Dominates
IBIT captured $306 million of May 19’s $667.4 million single-day inflows, extending its net inflow total to $45.9 billion. The fund’s 30-day inflow streak demonstrates sustained institutional demand, particularly from pension funds and asset managers rebalancing portfolios.
Farside Investors data shows IBIT now holds approximately 3.5% of Bitcoin’s circulating supply. This accumulation aligns with Bitcoin’s price stability above $100,000 for 11 consecutive days through May 20, before reaching a new all-time high of $112,000 on May 22.
Fidelity’s FBTC Gains Traction
While BlackRock leads, Fidelity’s Wise Origin Bitcoin Fund (FBTC) has emerged as a strong competitor. Though specific figures aren’t disclosed in recent filings, analysts estimate FBTC captured 25-30% of May’s institutional inflows based on CME open interest data.
The fund’s appeal stems from its lower 0.25% expense ratio compared to IBIT’s 0.30%. This price war between ETF providers has intensified as volumes grow, with combined assets under management across all spot Bitcoin ETFs now exceeding $150 billion.
Basis Trade Mechanics Fuel Growth
Three key factors drive the current ETF boom:
- 9% annualized yield from basis trades
- CME futures open interest up 30,000 BTC since April
- Institutional comfort with regulated crypto derivatives
Nexo’s Stella Zlatareva notes this activity signals Bitcoin’s transition from “alternative” to “benchmark” asset. The strategy’s popularity explains why ETF inflows haven’t created significant sell pressure—most institutional buyers immediately hedge futures exposure.
Recent blockchain data reveals a $1 billion Bitcoin withdrawal from Coinbase on May 9, likely tied to ETF custodian movements. Such large-scale transfers typically precede periods of heightened derivatives activity, as seen in current CME volume spikes.
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Market Impact and Future Outlook
The ETF frenzy has fundamentally altered Bitcoin’s market structure. With 15-20% of circulating supply now held in regulated investment vehicles, price discovery increasingly ties to traditional market hours rather than 24/7 crypto trading.
Analysts warn the basis trade’s popularity could increase volatility during market shocks. However, most institutions view the current 6-9% yield as adequate compensation for this risk, especially compared to traditional fixed-income alternatives.
As CME open interest approaches 158,000 BTC (worth $16.8 billion at current prices), the stage is set for Bitcoin’s next major price movement. Whether driven by macroeconomic factors or ETF flow dynamics, one truth emerges clear: Wall Street’s Bitcoin experiment has moved beyond proof-of-concept into mainstream adoption.
