While some investment commentators might question how far further "passive" products can go if markets stall, there is so far no end in sight to the rise in the size of these index-tracking entities.

Assets invested in exchange traded funds and products listed globally rose to $4.103 trillion at the end of May, based on preliminary industry figures.

The industry had 6,889 ETFs/ETPs, with 12,970 listings, from 313 providers listed on 68 exchanges in 55 countries at the end of May 2017, according to ETFGI, an organisation tracking the sector. The rise in assets happened against a backdrop of mixed fortunes for various markets last month.

ETPs are similar to ETFs in the way they trade and settle but do not use an open-end fund structure. The use of other structures including unsecured debt, grantor trusts, partnerships, and commodity pools by ETPs can, in addition to a significantly different risk profile, create different tax and regulatory implications for investors when compared to ETFs, which are funds.

“The performance of US equities was mixed in May. The S&P 500 gained 1.41 per cent while smaller cap equities declined 2.31 per cent. S&P 500 Growth was up 2.83 per cent while the S&P 500 Value index declined 0.32 per cent,” the report said.

Political risks remain a focus for investors - the ability of the Trump administration to move forward on policy goals and hearings on Capitol Hill, the UK election, North Korea is still an area of concern and the potential Italian election later this year is raising concerns similar to those raised before the French election,” Deborah Fuhr, managing partner at ETFGI, said.

ETFs and ETPs listed globally gathered record net inflows of $48.26 billion in May, marking the 40th consecutive month of net inflows. Year to date, a record $283.91 billion in net new assets have been gathered.