Borrow Rate Spike
In plain terms
When the cost to borrow a stock spikes, shorts are paying premium to bet against it — usually a bearish signal, except at extremes where they get squeezed.
How it works
When the cost to borrow a stock spikes, it signals either (a) shorts have HIGH conviction despite paying premium — bearish continuation — or (b) utilization is hitting recall risk — bullish squeeze setup. Two readings: Z-SCORE BREAKOUT (borrow fee z > +2 vs 60d baseline → short the stock) and SQUEEZE TRIGGER (borrow fee at extreme AND price reverses up → long the squeeze). Sourced from `stock_borrow_rates` (iborrowdesk daily, ~1y depth).
Live results
23 times picked on its own · 20 times inside a blend (10 beat the stock) · updated 2026-06-06Data dependencies
- Borrow fees (IBKR)
A data feed this strategy reads, refreshed on its normal schedule.
- Short interest
Bi-weekly NYSE/NASDAQ short-interest reports with days-to-cover.
Expected edge
- Reported return
- ~10% ann. on shorting expensive-to-borrow (Engelberg-Reed-Ringgenberg 2018)
- Tested over
- 2006-2014
Engelberg-Reed-Ringgenberg (2018) report ~10% annual on a long/short basket of cheap-to-borrow vs expensive-to-borrow stocks.
Example tickers where this is likely to fire
Illustrative only, the signal fires based on the live data, not a fixed list.
Related families
Watches FINRA's daily short-sale volume z-score. Aggressive new shorting in a falling tape = continuation; extreme highs that revert = squeeze fade.
If a stock has been on the SEC's 'failed-to-deliver' threshold list for many days, brokers are forced to close shorts — sets up a squeeze.
When THREE things fire together — expensive borrow, SEC threshold list, heavy FINRA short-volume — the stock sharply mean-reverts UP over 5 days.
Explore Borrow Rate Spike on alphactor.ai
See which tickers this family is currently firing on, with live signals and rankings.