BlackRock's iShares Bitcoin Trust (IBIT) led a wave of institutional withdrawals from U.S. spot Bitcoin ETFs on May 18, 2026, recording $448.36 million in outflows, according to SoSoValue data. The entire Bitcoin ETF complex recorded $648.64 million in net outflows that day, with not a single one of the twelve Bitcoin ETFs posting positive inflows. This represents the largest single-day outflow IBIT has recorded in recent weeks, signaling intensifying institutional selling pressure even on the world's most dominant Bitcoin ETF. The broader market context reflects sustained de-risking across crypto ETF products amid rising Treasury yields and risk-off sentiment following recent macroeconomic data.
## Daily Outflow Details
BlackRock's IBIT absorbed $448.36 million in withdrawals on May 18 alone. Ark Invest and 21Shares' ARKB followed with $109.64 million in outflows, marking the second-largest single-fund daily exit. Together, these two funds accounted for the overwhelming majority of the day's $648.64 million total drain.
IBIT shares closed at $43.45 on May 18, down 0.18% for the day. The fund has declined 13.6% year-to-date and 25.32% over the past twelve months, reflecting Bitcoin's price compression since its late 2025 peak near $71.82 per IBIT share.
## Cumulative Position and Market Share
Despite the single-day outflows, IBIT's cumulative net inflow since its January 2024 launch stands at $65.33 billion. Total Bitcoin ETF net assets have fallen to $100.49 billion, representing 6.52% of Bitcoin's total market capitalization. Cumulative net inflows across all Bitcoin ETFs total $57.69 billion.
IBIT maintains significant dominance with $62.2 billion in net assets and 4.04% share of total Bitcoin market cap, holding more Bitcoin than any other ETF by a significant margin.
## Ethereum ETF Pressure
Outflows extended beyond Bitcoin products. Spot Ethereum ETFs recorded $86.31 million in net outflows on May 18, marking the sixth consecutive day of withdrawals. This unbroken losing streak reflects sustained institutional de-risking across the entire crypto ETF complex.
## Market Context
Rising Treasury yields are directing institutional capital toward fixed income. Risk-off sentiment following recent macroeconomic data is reducing appetite for volatile assets broadly. Bitcoin has struggled to reclaim the $82,000 level, which would confirm a recovery above its 200-day moving average.
