S3 Short Interest Data

What it is

The institutional standard for lending-derived short-interest data, and the one product in this category a private investor cannot buy.

S3 computes what it calls revised short interest from custody data, prime-broker inventory feeds, regulatory filings and exchange data, with an in-house desk confirming rates from the voice-brokered financing market. The pitch is not that this supplements the exchanges' twice-monthly figure but that it replaces it.

The distinctive field is the borrow rate, and S3 is alone in publishing three of them: the offer rate a borrower pays, the bid rate custody banks charge prime brokerage, and the last rate for new shares. On top sit utilization, indicative availability, days to cover over 10, 30 and 90-day windows, and proprietary crowding, squeeze-risk and short-momentum scores plus a market-wide mark-to-market of short P&L net of borrow cost.

Pricing

Nothing is published. The AWS Data Exchange listing states that institutional pricing varies with the number of users in the enterprise; the vendor's trial page says data trials are complimentary and gives no duration; every other route ends at a sales address or a phone number.

One oddity, recorded rather than relied on: the same AWS Data Exchange listing that describes variable institutional pricing also carries a zero-cost subscription line with no end date. The two statements sit on one page and this card cannot reconcile them without subscribing. Do not plan around S3 data being free.

Data & coverage

Global — equities, ETFs and funds, corporate and government bonds, ADRs — with history since 2015. The security count is the one number to take with care: the AWS listing says more than 70,400, the product page says 65,000-plus and the company boilerplate says more than 50,000. Three figures for one dataset, all the vendor's own.

Updates are hourly on the feed specification: a start-of-day file at 08:00 ET and hourly refreshes from 09:00 to 17:00 ET. Fails-to-deliver is not among the datasets. The official FINRA and exchange figures are used as an input rather than sold as a product.

History is explicitly not point-in-time, which the vendor documents plainly. A revised series restates what it previously published, so anything backtested against it is testing on numbers that were not visible on the day.

Limitations

• There is no way for an individual to buy it. No price, no self-serve, and the retail channel is out of service.
• Not point-in-time. Disqualifying for a study that needs to know what was knowable then.
• Delivery is through somebody else's platform. Bloomberg, FactSet, Marquee, Snowflake or a file drop; the direct API has no public documentation, no published limits and no way in without a contract.
• Three security counts in the vendor's own material, and an update frequency that reads as real-time in marketing and hourly in the spec.
• No fails-to-deliver, and no insider or ownership data of any kind.

Alternatives

ORTEX is the self-serve competitor on the same idea — a lending-pool estimate with published prices from $39 a month and an API. ChartExchange sells the official filings, one broker's borrow fee and fails-to-deliver from $19.95 a month. iBorrowDesk covers borrow fees free. For short interest inside an ownership product, Fintel. The rest of the category is at insider, 13F and congressional trade trackers.