Assets in U.S.-based exchange-traded funds edged up $3 bn, or 0.5 per cent, in July to $578 bn, according to a report by State Street Global Advisors.

During the month, 17 new ETFs were launched and seven were liquidated, bringing the total to 708 as of July 31.

Micro-cap and small-cap ETFs had the greatest growth, up 38.6% and 17%, respectively. Fixed income ETF assets grew 5.4% and now represent more than 8% of total U.S. ETF assets. Assets of International ETFs, meanwhile, fell nearly $4 bn, or 2.8%.

Among industry sectors, energy lost more than $1 bn or 8.3%, while technology gained 9.5%, or $792 million. Assets in financial ETFs fell 3.4% to $383 m. Volume declined to $77 bn, down from $85 bn in June, SSGA said.