Trading data
Short interest and fails-to-deliver
A factual guide to short interest, days to cover, and fails-to-deliver — what each data point shows, how it is reported, and its timing limits.
What short interest measures
Short interest is the number of shares that investors have borrowed and sold, expressed as a share count or as a percentage of shares outstanding. It reflects bearish positioning — a bet that a price will fall — at a point in time.
Exchanges publish official short interest on a set schedule with a reporting delay, so the figure is periodic context rather than a live feed. Days to cover divides short interest by average daily volume to estimate how many trading days it would take to buy back the shorted shares.
Fails-to-deliver
A fail-to-deliver (FTD) happens when the seller in a trade does not deliver the shares within the standard settlement window. Fails occur routinely in normal markets and usually resolve quickly; the SEC publishes FTD data, and Regulation SHO sets locate and close-out requirements.
A short string of fails is ordinary settlement friction. Sustained, systemic fails can indicate stress and are examined separately, but the data is delayed and should be read with care.
What not to infer
High short interest does not mean a stock will rise or that a squeeze is coming. Short squeezes are rare and unpredictable, and many heavily shorted stocks trade flat for long stretches. A bearish bet is not evidence the bet is wrong.
Fails-to-deliver are not proof of manipulation, and short interest and FTDs are two different things. Treat both as delayed, partial data points — not timing signals.
Common questions
How current is short interest data?
It is reported periodically by exchanges with a delay, so it is point-in-time context rather than a real-time measure of positioning.
Is a high short interest bullish or bearish?
Neither on its own. It shows that investors have placed bearish bets. It is one data point to read alongside filings and financials, not a prediction.
Do fails-to-deliver prove illegal naked short selling?
No. Fails happen routinely and usually clear within days. Persistent systemic fails can warrant scrutiny, but isolated fails are normal settlement activity.