The $2.6 Billion Signal and the Geopolitical Ceiling

US spot Bitcoin and Ethereum ETFs recorded a net inflow of $2.6 billion in the week ending August 21, the largest weekly total since October 2025, according to Sosovalue data.

That reversed the prior week's $392 million outflow. Bitcoin funds alone brought in $1.9 billion over the five trading days, while ether funds added $697.2 million.

The inflows built steadily through the week: $297.6 million on Monday, August 17; $189.3 million on Tuesday; $517.2 million on Wednesday, the largest single day since May; and $606.3 million on Thursday, August 20, the biggest day of the run. BlackRock's IBIT alone accounted for roughly 83% of Thursday's total.

Bitcoin ETF trading volume for the week reached $22.1 billion, more than triple the prior week's $6.9 billion. Assets under management rose 25.4% to $96.1 billion, or roughly 6% of Bitcoin's total market value. Cumulative net inflows into US spot Bitcoin ETFs have reached $53.7 billion since they began trading in January 2024.

The Treasury Liquidity Trigger

The catalyst had nothing to do with crypto directly. On August 19, Treasury Secretary Scott Bessent said the department would raise the size of its long-term bond buyback operations to at least $4 billion per operation, part of an effort to bring down long-term borrowing costs, according to CNBC.