As observed in the table below, the S&P 500 has been dominated by just a few stocks in 2017. Through the end of last week, Apple alone was responsible for 13% of the market’s return. The top five contributors accounted for more than one-third of the market’s return. And the top ten contributors — representing just two percent of the 500 companies in the index —contributed nearly one-half of the return.
A robust market this has not been.
Source: Whitney Tilson