The combined market value of tech’s Five Fab — Apple Inc., Alphabet Inc., Microsoft Corp., Amazon.com Inc. and Facebook Inc. — was $2.4 trillion as of Dec. 27, or more than 11 percent of the S&P 500’s value. That means tech superpowers are inching toward the 16 percent share of the S&P 500 they held at the peak of the tech bubble in March 2000.