Recently, many friends have asked about how to view the U.S. stock market indices. In fact, the most confusing part of the U.S. stock market is that it’s not as simple as looking at the Taiwan Weighted Index. The U.S. capital market is so large, with numerous listed companies, so there are multiple indices representing different market aspects. The most important are the four major U.S. indices — the Dow Jones Industrial Average, S&P 500, Nasdaq, and Philadelphia Semiconductor Index.

Starting with the oldest. The Dow Jones Industrial Average was created as early as 1896, during America’s industrialization era, with only 12 companies at the time. Now expanded to 30 companies, covering various industries. Because it is a price-weighted index, the selection of component stocks considers not only company size but also whether the stock price would cause excessive volatility in the index. Apple, back then, had such a high stock price that it had to split before being included. For this reason, some believe that although the Dow is highly representative, it no longer fully reflects the overall U.S. stock market. It mainly represents traditional economy and blue-chip stocks, and better indicates economic stability.

As more companies went public, the S&P 500 was born. These 500 stocks account for about 75% of the total U.S. stock market capitalization, spanning major industries, from tech giants to everyday consumer brands. Because of its broad coverage and strict screening, the S&P 500 is regarded as the best “economic barometer” representing the health of the U.S. economy. If you want to grasp the overall direction of U.S. stocks, looking at the S&P 500 is more accurate than looking at the Dow.

Nasdaq was established in 1971 as a purely electronic exchange, mainly composed of tech stocks. As the tech industry grew stronger, this index gradually became a global tech market indicator. Many short-term traders treat Nasdaq as a “real-time market sentiment indicator.” When Nasdaq surges, it indicates market willingness to take risks and capital flowing into growth stocks; when it drops sharply, it often signals capital retreat. Moreover, Nasdaq’s movements are highly correlated with Taiwan stocks, making it an essential reference for investors watching Taiwan markets.

The Philadelphia Semiconductor Index was established in 1993, including 30 representative semiconductor companies. As demand for 3C products, cloud computing, AI, and other areas exploded, the market value of semiconductor stocks increased significantly, making the Philly Semiconductors Index the fourth major U.S. stock index watched globally. With TSMC also included in its components, the index’s rises and falls have a profound impact on Taiwan stocks.

Interestingly, these four indices often show different trends. A common scenario is Nasdaq falling while the Dow rises. This is actually capital rotating between sectors — selling off the overperforming tech stocks and shifting into the traditionally stable or defensive stocks that have fallen sharply. This does not mean the market is about to crash; it simply indicates capital repositioning. Conversely, when the Dow falls and Nasdaq rises, it usually reflects capital moving from traditional sectors to tech growth stocks. Therefore, investors should not only watch whether indices go up or down but also observe “who is leading the rally and who is leading the decline,” as the leading sectors reveal capital flow directions. When all four indices move in the same direction, the trend’s reliability is higher.

Regarding how to invest in these indices, there are mainly three methods. The first is ETFs, which track the index’s component stocks and weights, usually with lower management fees. Buying and selling are similar to stocks, but they cannot use leverage and can only go long. The second is futures, which have time sensitivity and leverage, typically settled every three months. Investors can put up margin and choose to go long or short to profit from price differences. However, because of leverage and the fact that U.S. stocks have no daily price limits, it’s recommended not to use the minimum margin, as wrong directions can lead to huge losses. The third is Contracts for Difference (CFD), similar to futures but without expiration dates, with higher leverage, making them more suitable for short-term trading.

Compared to investing in individual stocks, which face risks specific to each company, investing in major indices only requires selecting the overall country or region that is continuously growing. Indices like the S&P 500, which selects the top 500 companies by market cap, have an automatic “weed out the weak and keep the strong” function. In the long run, if the total market cap of these 500 companies exceeds the current level after 10 years, investors can profit. This is also a strategy highly endorsed by Warren Buffett.

If you want to invest long-term in the four major U.S. indices, you can do so through regular dollar-cost averaging into ETFs. But if you aim for short-term gains, futures and CFDs are better options, leveraging their ability to go both long and short, and using appropriate leverage for hedging or speculation. These tools are very suitable whether for risk management or trading. The U.S. stock market indices represent a global economic indicator, and regardless of which market you invest in, they are worth paying attention to.