A back-to-school tech-led sell-off. As if markets wanted to remind everyone the risks of interpreting stock market movements, major U.S. equity indices had a hard day on 03 September: the S&P 500 fell by 3.51%, the NASDAQ by 4.96% and the NASDAQ 100 by 5.23% over the day. Through this correction, markets have rekindled a long-standing question about the nature of the rally that resumed in March: Is it a bubble or not?