Mutual funds are still king with financial advisors, but they might soon lose their crown to exchange-traded funds as the top investment vehicle of choice in advisor asset allocations, according to a new survey from fintech company Broadridge Financial Solutions Inc.

The market size for U.S.-listed exchange-traded products—the vast majority being ETFs—is at $4.5 trillion and rising. Advisors have played a role in that growth by increasingly allocating toward these products in client portfolios.

Broadridge surveyed 513 financial advisors across the wirehouse, regional, independent broker-dealer and registered investment advisor channels. It found that 83% of respondents boosted their asset allocation to ETFs over the past two years, and 73% expect to increase their allocation in 2020.

And among those who plan to expand their ETF allocation this year, 55% said they will mainly shift assets away from actively managed mutual funds. That was followed by individual stocks (15%), passive equity mutual funds (14%), cash or equivalents (9%), and fixed-income bonds or mutual funds (5%). The remaining 2% comprises the amorphous “other” category.

The survey found that actively managed mutual funds remain the top product choice among respondents with an average asset allocation of 29%. ETFs are breathing down their neck at 27%, followed by individual securities (16%) and index mutual funds (10%). According to Broadridge, ETFs will likely surpass actively managed mutual funds in advisor asset allocation in the next few years.

ETFs have grown in popularity for several main reasons, including low costs, tax efficiency and the ability to diversify exposures in a tidy package. Of these, nothing comes close to low costs. Forty-nine percent of advisors in the Broadridge survey said that low costs was a reason to increase their use of ETFs, followed by tax efficiency (17%) and exposure diversification (13%). Only 9% cited performance as a reason to increase ETF usage.

RIAs are the most active ETF users among the various advisor channels included in this survey. Specifically, 44% of RIAs fit into the so-called heavy ETF user category defined as having more than 40% of assets under management in ETFs. The IBD/regional and wirehouse channels were at 23% and 14%, respectively.

And a little more than half of RIAs surveyed said they use ETFs mainly as core positions in client portfolios, which is significantly more than the other advisor channels.

Broadridge found that advisors much prefer broad market index ETFs over narrower product categories. The most popular types of ETFs used in client portfolios are based on a U.S. market index (95%), a foreign market index (73%) or have a sector/industry focus (68%). Bond funds are next at 62%.

Exchange-traded notes, along with ETFs based on exotic strategies including leverage, inverse structures and foreign currencies, bring up the rear with usage in the single-digit range.

And advisors still haven’t warmed up to thematic funds that focus on niche and/or cutting edge slices of the market in sectors such as blockchain, cannabis and artificial intelligence/robotics. Some investors use these products as satellite positions aimed at generating alpha within a portfolio’s overall equities sleeve. But according Broadridge, just 24% of advisors surveyed said they currently invest in thematic ETFs.

And among advisors who currently abstain from thematics, less than half say they definitely or probably will use these products.