Short Interest Diffusion Index (SIDI)

Measures the breadth of changes in short interest across a set of stocks. Rather than focusing on the total volume of short positions, the Short Interest Diffusion Index (SIDI) tracks the percentage of securities experiencing rising versus falling short interest. A high SIDI reading suggests that short-selling activity is increasing across many stocks, which may indicate growing market skepticism or bearish sentiment. Traders and analysts watch the SIDI for early warnings of potential market pullbacks or to identify sectors under broad-based short-selling pressure.