Still, just five stocks – Apple AAPL.O, Microsoft MSFT.O, NVIDIA NVDA.O, Tesla TSLA.O and Alphabet GOOGL.O - have accounted for about half of the index's gain since April, data published by Goldman Sachs earlier this week showed. Frazzled nerves have also been apparent in the Cboe Volatility Index .VIX, known as Wall Street’s fear gauge, which stands about 5 points higher than its long-term median. Investors next week will be watching U.S. consumer confidence numbers for a read on whether buyers are changing their purchasing habits in the face of worries of high inflation and COVID-19.