New Delhi, Aug. 17 -- The final minutes of the trading day used to be the Street's most crowded, as proprietary traders, retail investors, arbitrage funds and jobbers jostled with institutional investors for the winning trade.

The debut of the closing auction session (CAS) has flipped the script: trading has hit rock-bottom as most domestic traders and retail investors have stepped aside, turning the once-frenetic close into the leanest window of the day, a Mint analysis found.

Earlier this month, stock exchanges rolled out the 15-minute CAS system to determine official daily stock closing prices, replacing the decades-old 30-minute Volume-Weighted Average Price (VWAP) model.

Initially restricted to 213 stocks available for derivatives...