Octopus Energy was only set up in 2015 but has shaken up the energy market. Its website boasts of being the UK's "most awarded energy supplier" and promises cheap, renewable energy for households.

The most well-known measure of market sentiment is the CBOE Volatility Index, or VIX. The VIX measures expected price fluctuations or volatility in the S&P 500 Index options over the next 30 days.