Vanguard Group's fund inflows in the first nine months of the year were nearly $300bn, almost as much as in the whole of 2016, in the latest sign of the popularity of low-cost passive investing, writes Sarah Krouse for The Wall Street Journal.

The deluge of investor money has extended a successful period for the US investment company, whose assets topped $4tn for the first time at the end of January and have continued to swell to $4.7tn.