Today, August 10th, was supposed to be a landmark day for ChangXin Memory Technologies as it was officially added to the MSCI China All Shares Index. Based on its latest total market capitalisation, it is set to become the second-largest constituent in the index by market value, trailing only Tencent Holdings. Joining a list of names like Tencent, Alibaba, CATL, and Kweichow Moutai represents significant international recognition for a newly listed chip company and signals a future influx of passive investment funds. This should be unequivocally positive, right? However, the A-share market has its own temperament.

The stock opened at 52.47 yuan, declining immediately, then continued to fall, hitting an intraday low of 49.77 yuan around 1:10 PM, a drop of over 5%. Its total market capitalisation briefly fell below 3.43 trillion yuan. A giant, newly included in a top-tier global index and set to attract billions in passive investment, first drops 5% on the effective date. This script might feel familiar.

The "effective date curse" is not a new phenomenon. If you have followed MSCI's periodic adjustments, you know this "good news turning into bad news" scenario has played out many times in the A-share market. The reason is straightforward: expectations were already priced in. When MSCI announced the inclusion on July 28th, the market knew about it. From July 28th to August 10th, nearly two weeks, the anticipated gains and speculative sentiment were largely absorbed by the market. By the effective date, it becomes the window for early-positioned capital to "sell the fact" — with the good news realised, some naturally choose to lock in profits. Moreover, given the company's massive market cap after its first-day surge of 466%, the number of profitable positions is enormous. Any slight movement could trigger profit-taking.

But the story is more complex. After the drop exceeded 5%, a sharp recovery began. Around 1:10 PM, the stock hit its intraday low of 49.77 yuan and then rebounded quickly. By about 1:38 PM, the decline had narrowed to just over 3%, with the price returning to 50.84 yuan. The trading volume surged during this period, with the full-day turnover eventually exceeding 200 billion yuan. This raises a key question: who was buying at the 49.77 yuan level?

The answer likely points to a specific group: passive funds tracking the MSCI index. These funds do not seek excess returns; their goal is to minimise tracking error. Since MSCI’s China All Shares Index formally included ChangXin Memory Technologies today, these funds must complete their allocation of the stock on the effective date. They often use a common tactic: concentrated buying near the market close, known in the industry as the MOC (mark to close) strategy. By buying at the close, they can align their purchase price as closely as possible with the day's closing price, minimising tracking error. Historically, on MSCI adjustment effective dates, newly included stocks often experience a sudden spike in volume and a price surge in the final minutes. The stock's performance today is a textbook example of the "effective date effect" — profit-taking in the morning creates a dip, and passive funds enter in the afternoon to lift the price.

This process reveals a contest between two forces: active capital (profit-takers and speculators) and passive capital (index funds). Active capital, operating on a "buy the rumour, sell the fact" logic, seeks to realise profits at a high point after the positive news is confirmed. Passive capital, bound by the index composition, must buy regardless of the price, with no timing or judgment. Active capital wants to sell at a high price, while passive capital must buy today. The result is a large-scale exchange of shares in the range of 49.77 yuan to 50.84 yuan. Neither side is right or wrong; it is simply a collision of two different investment philosophies in the same stock.

In reality, today's volatility is minor for a company with a market capitalisation of 3.43 trillion yuan. The more significant long-term logic is worth noting. The company's inclusion in the MSCI China All Shares Index marks a shift from being priced solely by domestic capital to entering a phase of global index-based allocation. The funds tracking the MSCI China All Shares Index are estimated at around 300 to 500 billion US dollars. Even with a 1% weight, this could bring in 300 to 500 million US dollars in passive inflows, or roughly 2 to 3.5 billion yuan. This is just the beginning. Institutions expect the company to be included in the STAR 50 Index in September, the STAR Composite Index in October, and the CSI 300 Index by December next year. These indices also correspond to substantial passive fund flows. Once this series of index inclusions begins, the company could become a new anchor stock for major indices. From this perspective, today's MSCI inclusion is a starting point, not an endpoint.

Returning to the day's trading, the stock closed at 51.30 yuan, a decline of about 2.25%. For retail investors who panicked and sold in the morning, seeing the afternoon reversal might be disheartening. But for the passive funds that quietly accumulated shares near 49.77 yuan, they were simply completing a required task—buying enough shares to match the index weight and then closing out. This is a microcosm of the A-share market: the interpretation of information determines the direction of trading, and the trading direction in turn shapes the price movement. Inclusion in MSCI is positive, but positive news does not always equal an immediate price increase. When expectations are too high, the realisation can easily become a "sell the news" event. However, over a longer timeframe, the entry of international capital and the opening of index-based allocation for a company's valuation restructuring are never completed in a single day. So, is today's decline a tombstone marking "good news exhausted" or the beginning of a "golden pit"?