US equities are powering ahead once more. The S&P 500 is at its highs for the year, while the Russell 2000 smaller companies index, and the Dow Jones Industrial Average, are both at all-time highs. Even the Nasdaq Composite is up more than 10 per cent for the year.

The rally looks broad-based, but increasingly analysts are asking how long it can survive. The Chicago Board Options Exchange’s Vix index, which measures how much investors will pay to protect against future volatility, is at an all-time low – a sign of complacency.