**Name**
Institutional Herding Reversal Effect

**Hypothesis**
When a large number of institutional investors concentrate on buying a particular stock within a short period, it can create a "herding effect," potentially driving the stock price away from its fundamental value. However, such concentrated positioning is often accompanied by diminishing informational advantages and increasing liquidity needs. Once market sentiment reverses or a negative catalyst emerges, institutions might be forced to sell simultaneously, leading to sharp price reversals. Therefore, establishing short positions in stocks with a significant recent surge in institutional concentration and long positions in stocks where institutional ownership has stabilized after a period of disorderly selling may capture the alpha generated by this behavioral finance phenomenon.

**Implementation Plan**
Utilize data on changes in institutional ownership holdings. Calculate the quarterly change rate of institutional ownership and its cross-sectional percentile rank. Employ the `ts_rank` operator to identify stocks with abnormally high growth in institutional ownership (e.g., top 10%). Simultaneously, use the `ts_decay_linear` operator to apply time decay to selling pressure, identifying stocks where ownership has stabilized after a period of selling. Assign negative weights to the former and positive weights to the latter.

**Alpha Factor Optimization Suggestions**
The impact of institutional behavior varies across market cap styles (e.g., persistence might be stronger in large-caps, while reversal effects could be more violent in small-caps). Would it be beneficial to group stocks by market capitalization and calculate the abnormality of institutional behavior within each group to enhance the factor's robustness? Furthermore, incorporating overall market liquidity conditions (e.g., using the `trade_when` operator) to overweight this factor specifically during periods of tightening liquidity might better capture reversal opportunities arising from forced institutional selling.