The ETF industry saw a number of notable changes in 2015, including the rise of smart beta, more fee slashing, a spotlight on robo-advisors and a new milestone for growth when global exchange-traded fund assets reached $3 trillion in May. Here are some of the major ETF trends to watch in 2016:

The ETF juggernaut goes on. On a percentage basis, ETFs have been growing faster than mutual funds for years. That might be expected when comparing a relatively new industry to a mature one. 

But a new milestone was reached in the first quarter of 2015, when actual dollar growth in ETF assets sold through retail distribution channels exceeded mutual fund growth for the first time ever, according to Broadridge Financial Solutions. The vast majority of ETF asset growth has come from RIAs, independent broker-dealers, wirehouses and discount broker-dealers, according to Frank Polefrone, senior vice president of Broadridge’s Access Data products.

“We’ve seen a broad trend shift as more and more financial advisors use ETFs in lieu of mutual funds and individual securities,” says Polefrone. “This has been especially pronounced in the last year to 18 months.” He attributes the migration to ETFs to increased use of assets under management (AUM) fees over commissions, as well as greater awareness of index investing on the part of financial advisors and cost-consciousness among consumers. 

Most ETF growth has occurred since 2008 over a long, comparatively sedate bull market. But Broadridge data showed that over the year ending September 30, 2015, a period marked by substantial market volatility, ETF assets grew by $144 billion, or 7.4%. That growth was driven largely by retail channels. During the same period long-term mutual fund assets from third-party distributors declined by 2%, or $156 billion. 

“ETF assets continued year-on-year growth through the third quarter, despite the worst stock market drop since 2008, with advisors accounting for the lion’s share of investment,” says Polefrone. “The movement to ETFs and away from mutual funds is a big structural change, not just a fad.”

An opening for actively managed bond ETFs. Most actively managed ETFs are in the fixed-income category, but these newcomers still make up just a small fraction of the bond ETF universe. Because most of them are so new, they really haven’t had a chance to show their merit against bond indexes. 

But that could change if rates rise next year. Because of their market-cap weighting, most indexed bond ETFs are stuffed with U.S. Treasurys, which are highly sensitive to interest rate fluctuation. In theory, at least, actively managed funds should be able to adjust better to rising rates because they have a smaller percentage of assets in Treasurys and higher allocations to less rate-sensitive areas of the fixed-income universe, such as high-yield corporate and emerging market debt. They can also adjust portfolio durations to be longer or shorter than the indexes.

The giant in the space, the $2.7 billion PIMCO Total Return Active Bond fund (BOND), recently celebrated its three-year anniversary. This was the ETF that demonstrated the fatal flaw of funds with marquee manager names when it lost hundreds of millions of dollars soon after famed manager Bill Gross left PIMCO in September 2014. Nonetheless, its longer-term record is fairly impressive. Over the three years that ended September 30, its average annual return was 2.5% while the performance of the iShares Core Aggregate U.S. Bond (AGG), which follows the Barclays U.S. Aggregate Bond index, was 1.6%. The fact that BOND outperformed by nearly 1 percentage point annually, despite having an expense ratio 47 basis points higher than AGG’s, may convince investors that expenses are just one part of choosing an ETF.

The star power gap at PIMCO couldn’t have come at a better time for the SPDR DoubleLine Total Return Tactical ETF (TOTL), another actively managed offering. Launched in early 2015 the ETF, managed by bond guru Jeffrey Gundlach, holds some $1.6 billion in assets. Following on that success, State Street Global Advisors filed with the SEC later in the year for two more ETFs, also to be managed by DoubleLine Capital.