S&P 500 gains due largely to the likes of Apple and Facebook

Investors in passive S&P 500 index funds have Apple and Facebook to thank for much of their success so far this year.

That is the message from Fundstrat Global Advisors, which found that the $20tn benchmark US stock index owes much of its advance to a few dozen groups. The index’s 110-point rise this year has been driven mostly by 50 stocks, which have accounted for more more than four-fifths of that gain.

That includes the iPhone maker and Instagram owner, as well as ecommerce behemoth Amazon, Google owner Alphabet and cigarette maker Philip Morris International. The top ten contributors – which are rounded out by Johnson & Johnson, Visa, Microsoft, Oracle and Procter & Gamble – account for roughly half of the S&P 500′s rise.

Thomas Lee, the head of research at Fundstrat, noted that if you excluded the top 40 stocks that have contributed to the S&P 500′s 4.9 per cent rise this year, the index is “essentially flat”.

“Sector leadership has been notably defensive and concentrated,” he said in a note to clients on Monday. “Year to date, excluding the 10 best stocks…the S&P 500 is up ~2 per cent. [The] market is a lot more concentrated than most realise.”