As far as the top performers in the restructured suite, Bartolini said investors had been favoring international plays.

For example, the SPDR Portfolio Developed World ex-US ETF (SPDW) added $1.4 billion in assets since the funds were restructured.

On the U.S. equities side, the SPDR Portfolio Total Stock Market ETF (SPTM) has witnessed 175% growth in AUM.

“It started at $520 million in assets – it’s taken in $900 million in assets – it’s up to $1.4 billion,” Bartolini said. “The fund with the biggest growth, which points to more usage in portfolios – is SPDR Portfolio Large Cap ETF (SPLG). It had $155 million in assets when we restructured. Now it has $1 billion. Those assets grew by 580% since we restructured the funds.”

The Portfolio ETFs are among the cheapest ETF options on the market, contending with other low-cost players like Charles Schwab, BlackRock’s iShares and Vanguard. To put ETF costs in perspective, there are 2,029 U.S.-listed ETFs on the market with an average expense ratio of 0.58%.

The group of 15 SPDR “Portfolio” ETFs expense ratio ranges from 0.03% to 0.11%.

For more information, visit https://us.spdrs.com/en/strategies/spdr-portfolio-low-cost-etfs.