India's new closing auction system, which determines the official closing prices for stocks in the futures and options (F&O) segment, has caused significant volatility and concern among market participants. This system, which operates from 3:15 pm to 3:35 pm, replaces the previous volume-weighted average price (VWAP) method and aims to improve transparency and price discovery. However, the initial rollout has led to divergences between the Sensex and Nifty indices, and unexpected price movements, especially on derivative expiry days.
Concerns are particularly pronounced for the Sensex due to lower cash market participation during its auction window compared to the NSE, making it potentially more susceptible to large trades. Traders are worried that low liquidity in the closing auction could allow even small price movements in heavyweight stocks to disproportionately impact the index's closing level and, consequently, derivative settlements. This has led to anxieties about distorted settlement prices, which could result in permanent gains for some and losses for others.
Several brokers have advised retail clients to close their equity and derivative positions before 3 pm to avoid the unpredictable nature of the closing auction. There's a fear that if genuine investors and liquidity providers avoid the auction, liquidity could thin further, creating a self-reinforcing cycle of weaker liquidity and poorer price discovery. Analysts, however, generally anticipate that the volatility will be temporary as market participation improves and the mechanism becomes more efficient over time. The Securities and Exchange Board of India (SEBI) has not yet commented on the divergence between the benchmark indices.
