Sometimes a good thing can turn into a bad thing if it is too good. Some portfolios are too concentrated on these winners after the shares of America's five tech giants continue to hit record highs, and some strategists now believe that the market may turn in the future, which is disturbing.

Holding shares in AAPL (AAPL), MSFT (MSFT), AMZN (AMZN), Facebook (FB) and Alphabet (GOOGL) have rewarded investors handsomely, with their shares rising between 125% and 245% since the beginning of 2019. The shares of these five companies are widely held not only by index investors, but also by a wide range of active fund managers, including those who do not usually hold growth stocks.

Taken together, these five companies account for nearly 22% of the S & P 500. The "Nifty Fifty" dominated in the 1970s, while in the 1980s it was dominated by blue chips such as IBM (IBM) and AT&T (T). Howard Silverblatt, a senior index analyst at S & P Dow Jones Indices, believes that while these companies may have had more influence on the economy than the largest companies today, the stock market is more concentrated now than in the past, and the big five tech giants have a much greater impact on the market because of their size. Apple and Microsoft are the first U. S. stocks with a market capitalization of more than $2 trillion.

Apple's weight in the S & P 500 peaked at about 7 per cent in 2020 (it fell slightly in 2021), higher than the weight of IBM in its heyday.

There are signs that investors' risk appetite is waning, which could hurt the growth prospects of large technology companies. There has been a sell-off in more speculative areas of the market, such as cryptocurrencies and special purpose buyout companies (SPAC), and investor concerns about inflation and rising interest rates are growing. If the big five tech giants slow down or plummet, the entire market, including all index investors, will be affected.

Goldman Sachs gives an example: if the shares of the five tech giants fall 10 per cent, the bottom 100 stocks in the index must rise 75 per cent if the s & p 500s are to remain flat. This dynamic explains why narrowing the width of the market usually causes huge losses.

Investors' portfolios are full of these five stocks, and once the market turns, it will be difficult for them to protect themselves by diversifying their holdings. The momentum of these five stocks has begun to slow. Amazon, for example, accounts for about 4% of the S & P 500, surpassing the energy, real estate, materials or utility sectors. Amazon shares, which have not hit an all-time high in 2021, outperformed the S & P 500 by 25 percentage points because of questions about the company's e-commerce growth since September 2020. Coupled with regulatory pressure, the road ahead for the five giants is likely to be even more bumpy.

The global economic recovery may also make the five stocks less special. Scott Opsal, director of research at Leuthold Group, said: "the trend of large technology stocks has been benefiting from weak economic growth and low interest rates. Investors want to hold some stocks with strong growth, but for those who think the economy has room for growth, they no longer have to invest in such high-priced stocks. Oppsar believes that the changing economic and market environment is the reason why investors should now adopt a barbell investment strategy-holding not only some of the winners of technology stocks, but also some value-oriented stocks and small-cap stocks. Make your investments more diversified.

Oppsar said that because the stock market is highly concentrated on a few large technology stocksInvestors should choose funds that are willing to deviate from their conventional track, growth or extreme value.

It is not easy to find good fund managers. They need the sharpness to choose the right stocks in addition to the other 495 stocks, the courage to find new ways, and a track record to prove to investors that they are different and right. The performance of some fund managers does not look so good because they have cautiously reduced their holdings of technology stocks, which have pushed the market to highs in the past few years. In addition, not holding any or even a small amount of shares in technology companies can sometimes cause these fund managers to fall out of Morningstar's related fund category.

High active specific gravity (active share) is usually the preferred indicator for fund managers who are willing to deviate from the benchmark index.While this is a good place to start, being different doesn't always mean winning, so Morningstar strategist Alec Lucas (Alec Lucas) advises investors to learn about the ideas behind the stocks and stock selections in fund managers' portfolios, and when they buy and sell stocks.

Investors should try to get more diversified investments while investing in large growth companies.