Apple, Microsoft become S&P 500's biggest duo in decades

Apple Inc. and Microsoft Corp. play a bigger role in the S&P 500 Index these days than any two companies have in decades. The maker of iPhones and the supplier of Windows software accounted for 12.5% of the index’s value between them as of Tuesday. Their combined weight exceeded every year-end total for the S&P 500’s top two companies since 1980, according to data compiled by Bloomberg and S&P Dow Jones Indices LLC. International Business Machines Corp. and American Telephone & Telegraph Co. together were 10.9% of the index in 1982, before AT&T was broken up.