Short Interest
Short interest is the total number of shares of a given stock that have been sold short and not yet covered or closed out, typically expressed as a percentage of the total shares available for trading (the float) and published twice monthly by FINRA.
When a market participant sells a stock short, they borrow shares from a broker and sell them in the open market, hoping to repurchase them later at a lower price to return to the lender and pocket the difference. Every short sale that has not yet been closed — meaning the borrowed shares have not yet been repurchased — adds to the total short interest outstanding in that stock. This cumulative figure is a widely tracked data point that provides insight into the bearish positioning of market participants.
In the United States, short interest data is collected by FINRA and the major exchanges and published on a twice-monthly schedule. The data shows the total short interest (in shares) as of specific settlement dates — typically mid-month and end-of-month. Many financial data platforms convert this raw share count into short interest as a percentage of float, which is the more analytically useful metric for comparison across stocks of different sizes.
A short interest ratio — also called 'days to cover' — is calculated by dividing the total shares sold short by the average daily trading volume. A days-to-cover figure of 5 means it would take 5 days of average trading volume for all short sellers to repurchase their shares simultaneously. High days-to-cover ratios (above 8 to 10) can be significant because they indicate that any forced covering would take an extended period to absorb, potentially creating severe upward price pressure — the setup for a short squeeze.
High short interest can mean different things in different contexts. In a heavily researched, liquid large-cap stock, high short interest often reflects fundamental disagreement — some sophisticated investors believe the stock is overvalued or that the business fundamentals are deteriorating. In a thinly traded small-cap, high short interest may reflect speculative positioning based on negative momentum. The identity of who is short matters enormously: institutional short sellers with detailed research behind their positions are very different from retail traders shorting based on momentum or social media narrative.
Short interest data is publicly accessible through FINRA's website and is incorporated into major financial data providers like Bloomberg, FactSet, and S&P Global Market Intelligence. For individual stocks, the short interest data releases twice a month but the actual short position changes continuously as traders enter and exit positions between reporting dates, meaning the published data is always somewhat lagged relative to current conditions.