Some of the most important technology stocks listed on the S&P 500 are going through a major shake-up on Monday, September 24. Mega-corporations such as “Alphabet Inc., Facebook Inc., Netflix Inc.,” will be moved from the technology and consumer discretionary sectors and placed into the new comprehensive “communication and media stocks” sector. According to a report from Reuters, this move is the most substantial change to the Global Industry Classification Standard (GICS) in history.

“The last several years have seen an evolution in the way we communicate and access entertainment content and other information,” said a representative of the S&P Dow Jones last year after the shake-up was first announced. “This evolution is a result of integration between telecommunications, media, and internet companies,” he added.

The S&P Dow Jones also stated that the reclassification “is a step toward acknowledging the convergence of telecommunications, media, and select internet companies and the overlapping services rendered by these companies, within the GICS Structure.”

Although several stocks are changing classifications, “Facebook, Netflix, and Google-owner Alphabet,” are the ones many investors are watching the closest. These stocks comprise three of the four companies that form the “FANG stocks,” with the fourth stock being Amazon. These stocks are some of the most dominant in the technology sector, with many experts attributing tech’s meteoric rise in large part to these four corporations.

Although this reorganization is predicted to cut tech’s share of the S&P 500 from 26 percent down to 20 percent, the sector will still have heavy hitters such as Apple Inc., Microsoft Corp, Visa Inc., and Intel Corp. This move should allow these corporations and more niche firms to gain greater market visibility.

In addition to the three FANG stocks, the new communication and media sector will now encompass companies such as CBS, Walt Disney, News Corp., and Twitter, among others. According to CNBC, this move should produce major changes to “stock ownership” as investors restructure their portfolios.

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With money managers suddenly faced with portfolios light on tech, there could be decisive gains in the tech sector as investors scramble to fill the newly created void.

“It is very important for investors to understand how the reclassification will affect their portfolios, since the ETFs that they currently hold may no longer suit their investment objectives,” said Zacks Investment Research’s director of ETF research Neena Mishra, during an interview with CNBC.

With the new reclassification looming in the immediate future, the S&P 500 closed down, but by less than 0.1 percent according to Market Watch. The NASDAQ also finished in the red by half of a percent; however, the Dow Jones industrial average hit a record high at close for the second day in a row.

Surprisingly, the markets have largely ignored the new tariffs being placed on Chinese imports.