It begs the question: How much longer can this last?

Exchange-traded fund and exchange-traded product investing has reached record level highs during the first seven months of 2017, according to independent research and consultancy firm ETFGI, fuelling concerns that there is a passive investment "bubble" about to burst.

ETFGI said that investments into the global ETF/ETP ecosystem have reached highs of $391.3 billion, which is a billion more than what was invested in all of 2016. In July, ETFs and ETPs listed globally gathered $43.48 billion in net inflows, which marks 41 consecutive months of net inflows.

As the ETF/ETP sector continues to grow, thoughts are growing to whether this is sustainable in the financial market, and whether it could an industry “bubble”.

More and more firms are launching ETFs, including asset management firm Blackrock, which launched four in the month of July as reported by this publication.

(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.)