The top 5 tech stocks confound index skeptics, as their earnings beats drive the S&P 500 to even greater concentration

Five stocks — Microsoft, Apple, Amazon, Facebook and Google — now account for 21.65% of the S&P 500. During the tech bubble, the top 5 stocks in the S&P 500 only reached 18% of the index.

Over the last month, these 5 stocks’ share of the S&P 500 has grown, driven by Q2 earnings beats. While the popular S&P 500 ETFs from StateStreet (NYSEARCA:SPY), iShares (NYSEARCA:IVV), and Vanguard (NYSEARCA:VOO) are up 5.9% versus a month ago, Apple is up 16.51%, Amazon 14.71%, and Facebook 11.71%. Alphabet / Google’s share price slightly underperformed the index with a 4.93% increase over the last month, and the only major laggard is Microsoft, up only 0.74%.

The market cap weighted S&P 500 index, with all its concentration in the top 5 tech stocks, is once again outperforming the equal-weighted version of the S&P 500. Over the last month, the ETF for the equal weighted version of the index (NYSEARCA:RSP) rose 0.5% points less than the market cap weighted ETFs.

This is confounding those who argue that the market cap weighted S&P 500 is becoming useless due to its concentration in the top 5 tech leaders. And the outperformance of the top 5 stocks is making it harder for fund managers who don’t have sufficiently concentrated positions in Microsoft (NASDAQ:MSFT), Apple (NASDAQ:AAPL), Amazon (NASDAQ:AMZN), Facebook (NASDAQ:FB) and Google (NASDAQ:GOOG) to beat the index.

For more, see the exact breakdown of SPY’s top 10 holdings, and this remarkable tirade against the index by a fund manager.