The Nasdaq 100 is going to be replaced again, which is also one of the reasons why I pay attention to index investment. Before the opening of the US stock market on October 9th, Moderna (MRNA) will join the Nasdaq 100 index, replacing Warner Bros. Exploration (WBD). First of all, let me clarify that this adjustment is for the Nasdaq 100, not the Nasdaq Composite Index. Many people think of Nvidia, Apple, and Microsoft when they see Nasdaq. Moderna, which joined this time, is a biotechnology company with mRNA technology as its core. This also reminds us that the Nasdaq 100 is not a pure technology industry index, it covers eligible Nasdaq listed large non-financial companies. However, what is more worth discussing than 'who enters and who exits' is that the index will continue to adjust its members. To buy a company, you need to constantly assess its competitiveness, whether its business has changed, and whether it is worth continuing to hold on to. Buying an index means accepting a set of publicly available rules that allow the portfolio to update as the constituent stocks adjust. Holding for ten years does not mean that you will always hold the same batch of companies during that time. For ordinary investors who are not good at studying each company, this mechanism can indeed reduce some of the burden of stock selection. But don't understand it as' automatically eliminating bad companies, always buying good companies'. The index adjustment is based on the compilation rules, not predicting for investors who will rise the most in the future. Being included does not mean that the stock price is cheap; Being eliminated does not mean that the company will not have opportunities in the future. For Moderna, inclusion in the index may bring about a demand for tracking fund allocation, but between the announcement and its implementation, the market will also trade this expectation in advance, and it cannot be simply concluded that "buying on October 9th will make money". For those who hold funds that track Nasdaq 100, they usually do not need to sell their WBD and buy MRNA separately. The foundation will adjust their tracking strategy accordingly. So, the inspiration this incident gave me is not to hurry up and chase after a new member. But when we hold the index for a long time, we hold a set of updated portfolios, rather than betting that a certain company will always be ahead. Of course, portfolio updates do not mean that valuation risk and market pullback will disappear. The burden of stock selection can be entrusted to the rules, positions, and time spent on money, but it still needs to be managed by oneself.