ETF and ETP assets increased 7.3 per cent from $1.95 trillion to $2.09 trillion during the first quarter, according to figures from UK-based research company ETFGI.

ETFs are typically open-ended, index-based funds which can be bought and sold like ordinary shares on a stock exchange. They offer exposure across developed, emerging and frontier markets, equities, fixed income and commodities. ETPs, meanwhile, are similar to ETFs in the way they trade and settle but do not use an open-end fund structure.

The market has expanded rapidly in recent years, with some wealth managers saying they expect further growth in these "passive" vehicles. There have been some concerns: some "synthetic" products, which use swap-based techniques to replicate market returns, have raised concerns about counter-party risk. 

Both sets of investment vehicles recorded $23.9 billion in net inflows in March 2013. Equity ETFs and ETPs gathered the largest net inflows with $17 billion, the data showed.

Some $16.6 billion was invested into US/North America exposure, followed by $5.3 billion into developed Asia-Pacific, while emerging market equity experienced a net outflow of $5 billion.

Fixed income ETFs and ETPs saw inflows of $5.6 billion, with high yield gathering the largest net inflows of $1.6 billion, while money market ETFs and ETPs experienced net outflows of $665 million.

Commodity ETFs and ETPs saw net outflows of $2.6 billion in March 2013. ETFs and ETPs providing exposure to precious metals experienced the largest net outflows of $2.1 billion, while broad commodity ETFs and ETPs gathered the largest net inflows of $211 million.