As December approaches, major index constituent stocks are set for an adjustment. As a star index in the market, every change in its constituents attracts investor attention. Based on current predictions from major securities firms, the CSI 300 Index is expected to see adjustments involving 17 stocks this time.

The periodic review of index constituents generally consists of three stages. Stock indices are reviewed every six months, typically in May and November each year. The reference data cutoff for these adjustments is usually one and a half months before the implementation date. The adjustment list is announced 2-3 weeks before the implementation date, with new constituents taking effect on that day.

The review criteria, timing, and implementation schedules for the CSI Index Series and SSE Index Series are aligned. The May review uses data from May 1 of the previous year to April 30 of the current year, with adjustments taking effect on the trading day following the second Friday of June. Similarly, the November review covers data from November 1 of the previous year to October 31 of the current year, with adjustments implemented on the trading day after the second Friday of December.

According to the rules of the China Securities Index Company, stocks must meet strict criteria to enter the sample universe, including listing duration (non-ST/*ST stocks, with at least one year for STAR Market/GEM listings and one quarter for others), average daily trading volume (top 50%), and average daily market capitalization (top 300 for CSI 300, ranks 301-800 for CSI 500). Additionally, a "buffer rule" (e.g., new stocks ranked within the top 240 for CSI 300 are prioritized for inclusion, while existing constituents ranked within the top 360 are retained) helps minimize frequent adjustments.

For example, the reference period for the December 2025 CSI 300 adjustment spans from November 1, 2024, to October 31, 2025. Stocks with significant market cap growth and sufficient trading volume during this period are more likely to be included.

In recent years, as investor acceptance of index-based investing has grown, index fund assets have expanded significantly. From Q1 2010 to Q3 2025, equity ETF assets showed an overall upward trend, reaching RMB 4.11 trillion by the end of Q3 2025. Meanwhile, conventional equity index funds (excluding ETFs) saw slower growth due to factors like the phase-out of structured funds, though a slight rebound occurred in Q3 2025.

As of October 31, 2025, passive and enhanced index funds tracking the CSI 300 Index reached RMB 1.3509 trillion, while those tracking the CSI 500 Index totaled RMB 229.5 billion, and those tracking the STAR 50 Index amounted to RMB 183.2 billion.

"Since 2020, stocks added to or removed from the CSI 300 and CSI 500 indices have shown significant cumulative excess returns relative to the index itself in the 60 trading days before and after the adjustment. The market tends to price in the impact of index changes early, as investors can predict likely adjustments based on rules and trade ahead, leading to opposite price movements—rising before inclusion and falling before exclusion," analyzed Wei Jianrong, head of financial engineering at Kaiyuan Securities.

As a barometer of the A-share market, the CSI 300 Index is expected to see 17 adjustments this time, concentrated in sectors like power equipment, electronics, and transportation. The 17 potential new constituents include Huadian New Energy, Shenghong Technology, Shanghai Electric, Guangqi Technology, Ningbo Port, Rockchip Microelectronics, Huagong Tech, Dongshan Precision, Enlight Media, Compass, Anker Innovations, Guolian Minsheng, Toppan Printing, Zhongtian Technology, Sanan Optoelectronics, Hainan Airlines, and Sinopharm Xinwei.