Sensex gains 0.6% while Nifty 50 crashes over 1%: Decoding the unusual market divergence | Stock Market News
Domestic market benchmarks displayed a rare feat on Tuesday, 4 August, when the 30-share pack Sensex jumped over 0.60%, while the NSE barometer Nifty 50 plunged over 1% during the session. This sharp divergence in the frontline indices perplexed investors.
In the previous session, the Sensex rose 544 points, or 0.70%, to end at 78,639, while the Nifty 50 jumped 391 points, or 1.60%, to settle at 24,774.30. The Nifty surged nearly 201 points in the final two minutes of Monday's trade, thanks to the implementation of the Closing Auction Session (CAS) in the equity cash segment, which became operational on the same day.
The same factor is driving the divergence in benchmarks on Tuesday, also.
"Due to the recent change in closing mechanism, Nifty spot witnessed a nearly 200-point surge in the final closing figures on a single tick, whereas Sensex spot and futures both settled fairly on Monday. Today’s divergence is simply a normalisation of the previous session’s anomaly—with Nifty spot down over 1.0% while Sensex is trading flat," Vipin Kumar, AVP-Research at Globe Capital Market, explained.
Market regulator Securities and Exchange Board of India (SEBI) has designed a new auction-based mechanism to make the price discovery process more transparent.
As per experts, the main objectives behind this mechanism are to improve end-of-day price discovery, make closing prices more resistant to manipulation, better reflect actual demand and supply at the close, and align India's markets with global exchanges that already use closing auctions.
The reform was announced through a circular on 16 January 2026 and came into effect on August 3, 2026, initially for stocks in the futures and options (F&O) segment. The existing volume-weighted average price (VWAP)-based methodology will continue for other stocks.
Under the new framework, the Closing Auction Session will be conducted every trading day from 3:15 PM to 3:35 PM, immediately after the regular market closes at 3:15 PM. During this 20-minute window, investors can place market and limit orders to help determine the official closing price of eligible stocks.
The order entry window will close at a random time between 3:28 PM and 3:30 PM, with the exact time determined automatically by the exchange's system. This random closure is intended to prevent last-minute manipulation of stock prices.
While the cash market's closing auction ends at 3:35 PM, trading in the equity derivatives segment continues until 3:40 PM.
After the auction, a post-close session will be held in the cash market from 3:50 PM to 4:00 PM, during which investors can buy or sell shares only at the final closing price discovered through the Closing Auction Session.
In a media statement on 3 August, NSE said the Closing Auction Session is made applicable in a phased manner. Initially, from 3 August 2026, the closing price of stocks in the cash segment on which derivative contracts are available is determined based on CAS.
The closing price for the remaining securities in the cash segment continues to be determined based on VWAP of the trades executed during the last 30 minutes of the CTS (Continuous Trading session) in the cash segment.
On the first day itself, 515 trading members participated, and they placed orders for 56,773 unique PANs, NSE said.
Disclaimer: This article is for educational purposes only and does not constitute investment advice. The views and recommendations expressed are those of individual analysts or broking firms, not Mint. We advise investors to consult with certified experts before making any investment decisions, as market conditions can change rapidly and circumstances may vary.
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