Bitcoin ETFs took in $6.2m last week and gained $4.95bn

American spot bitcoin ETFs closed the week of 14 to 18 September with a net inflow of $6.21m, according to SoSoValue's daily series. Over the same five sessions the assets held in those funds rose from $97.58bn to $102.53bn. Both numbers are correct, and the distance between them is the story.

The week ran like this:

• Monday: plus $160.0m. Tuesday: minus $450.3m. Wednesday: minus $296.0m.
• Thursday: plus $159.5m. Friday: plus $433.0m.
• Week: plus $6.21m on $16.17bn of trading.

Friday's inflow of $433.0m and Tuesday's outflow of $450.3m are $883.4m apart, which is 142 times the figure the week finished on. The net result came out of $16.17bn in turnover, so 0.038% of everything traded stayed in the funds. A week earlier the same products had lost $462.7m net, so the outflow stopped rather than reversed.

Where the $4.95bn came from

Set the $6.21m against the $4.95bn the asset base gained and new money accounts for 0.13% of the increase. Price did the rest. The same split shows up on the long view: cumulative net inflow since these funds launched is $55.16bn, while they hold $102.53bn, so $47.37bn of what sits in them, 46.2% of the total, was never deposited by anyone. It is appreciation on coins bought earlier.

Ether ETFs moved the other way in the same five days, closing at minus $140.0m. Three consecutive negative sessions from Tuesday to Thursday took out $404.8m and ended a four-week run of inflows. Relative to size the contrast is sharper than the headline figures suggest: the bitcoin funds' net week was 0.0061% of their assets, the ether funds' was 0.84% of theirs, which is 137 times larger in proportion. Ether's own asset base still rose 2.54% over the week, meaning price had to cover the withdrawal and the gain both.

“Incredible intestinal fortitude from the Boomers given they saw a 50% drawdown.”

— Eric Balchunas, Bloomberg ETF analyst, quoted by The Block

Eric Balchunas, Bloomberg ETF analyst, on why holders have stayed

What the cumulative line says

The cumulative line is where the drawdown he refers to is visible. It peaked at $62.77bn on 9 October 2025 and stands at $55.16bn now, which is $7.61bn and 12.1% below the top. Money has left these funds on net over eleven months while the assets under management went up, which is the same arithmetic as the week just gone, stretched out. We measured the long version of this on the first bitcoin ETF's fifth year.

Bitcoin ETF weekly flows are worth reading for one thing in the days ahead: whether the net stays near zero while the assets keep moving. Flat flows with rising assets mean existing holders are sitting still, not that new buyers arrived. Who actually holds bitcoin, as opposed to who is said to be buying it, is a question we put numbers on for state reserves.

Informational material, not investment advice. Flow and asset figures are SoSoValue data for US spot ETFs through the close of 18 September 2026; percentages are our own calculations.