A chart shows a large volume of short sales yesterday, while another page reports a much smaller short-interest figure. The difference is not enough to conclude that one dataset is wrong. They may be counting different things over different periods.
FINRA’s explanation of short interest distinguishes a snapshot of outstanding short positions from the volume of transactions executed as short sales. A position opened and closed during the same day can contribute to trading volume without remaining open at a later reporting snapshot.
FINRA also describes coverage limits in its daily volume data, including its off-exchange scope. A figure copied onto another website therefore needs its original definition, not just a new chart title.
Read four labels before drawing a conclusion
- What is being counted: open shares, traded shares or a calculated ratio?
- Which date does the figure describe, and when was it published?
- Which venues and transactions are included?
- If a percentage is shown, what is its denominator?
Keep those answers beside the chart. A percentage of daily trading volume and a percentage of a share float cannot be compared as if they describe the same population.
Use a transaction diary as a thought experiment
Imagine a fictional position that is opened in the morning and fully closed in the afternoon. Write one line for the opening trade and another for the closing trade. Then ask separately what happened during the day and what remained open afterwards. This small exercise makes the difference between activity and a remaining position easier to see.
Do not add daily short-sale volumes together and label the sum outstanding short interest. The activity can include positions that no longer exist, while an older still-open position need not create a new short sale every day.
Neither measure alone predicts a price move or proves a trading strategy. Understanding the definition is the first step towards reading the data; it is not a recommendation to buy, sell or short a particular security.