Tuesday’s market rebound was inevitable after such a long series of declines, but only adds to the air of volatility. This follows a long period of relative calm. According to Ed Easterling of Crestmont Research, the volatility of the S&P 500 was running at just 6.2 per cent in April, less than half the average since 1950.

History suggests volatility moves through irregular but violent cycles, with periods where volatility is less than 10 per cent followed by jumps above 20 per cent. The last volatile period was from 1999 to 2003. According to Easterling, the US market has dipped below the 10 per cent volatility level on nine occasions since 1950. The average calm period lasted 16 months. As of April, the period of low volatility had lasted 27 months, the second longest since 1950.