Short Interest

Short interest is the standard way to compare short selling across companies. Dividing the aggregated net short position by total shares on issue removes the effect of company size, so a mid-cap with 40 million shares short and a large-cap with 400 million short can be ranked on the same scale. Every ranking on this site uses that percentage, calculated from the two fields ASIC publishes side by side: reported short positions and total product in issue.

There is no universal level at which short interest becomes notable. Most ASX-listed securities sit well below 1%. Anything above 5% is uncommon, above 10% is genuinely heavy, and the small group above 20% represents concentrated, high-conviction positioning. Context matters more than the absolute number — lithium, buy-now-pay-later and speculative resources names have historically carried structurally higher short interest than banks or infrastructure trusts, so comparing a stock against its own sector is more informative than comparing it against the market.

Because Australia reports net positions, short interest understates total short selling activity. Hedged and arbitrage strategies — convertible bond arbitrage, index arbitrage, merger arbitrage, market making — all generate short exposure that is partly netted away or is not a directional bet against the company at all. High short interest is evidence of positioning, not proof of a bearish thesis.

The T+4 publication delay means the figure describes the market as it stood four trading days ago. During fast-moving events, a profit warning or a capital raising, the published number can lag the real one materially. The trend across successive reports is usually more reliable than any single day, and a steadily rising line matters more than one large print.

Short interest is also the input to several derived measures. Divided by average daily volume it becomes days to cover, an estimate of how long the exits would take. Measured against free float rather than shares on issue it rises, sometimes considerably, because locked-up and strategic holdings are excluded from the denominator.