What’s striking is the role played by the biggest technology leaders, again reminiscent of the dot-com era. According to Bespoke Investment Group, Apple (AAPL), Facebook (FB), Amazon.com (AMZN), Microsoft (MSFT), and Alphabet (GOOGL) accounted for 4.6 of the 7.89 percentage-point gain this year in the S&P 500. Through Thursday, S&P data maven Howard Silverblatt calculated, the top 15 S&P 500 stocks generated half of the big-cap benchmark’s year-to-date increase. (What has changed is that Amazon and Alphabet both flirted with $1,000 share prices, while two decades ago stock splits were all the rage.)
Source: Bitcoin and Tech Stocks: A 21st Century Tulipmania? – Barron’s