Investors have already piled $705 billion into exchange traded funds over the first seven months of the year, bringing 2021 global ETF assets to a record $9.1 trillion.

According to Morningstar Inc. data, net flows so far in 2021 have almost eclipsed the $736.5 billion investors threw into ETFs globally for all of 2020, the Wall Street Journal reports.

The lion’s share of the cash infusion this year has gone into low-cost, index-based ETFs, with large cap and short-term bond ETFs, along with those offering inflation protection, bringing in significant investor interest.

The U.S. ETF market made up a record $519 billion of the total, bringing assets in U.S.-listed ETFs to about $6.6 trillion.

With this year’s inflows, ETFs now hold more money than index-based mutual funds, which hold about $8.8 trillion in assets as of June. Nevertheless, mutual funds overall still have $40.7 trillion in total assets under management.

“ETFs are probably the greatest success story in financial services over the last two decades,” Anaelle Ubaldino, head of ETF research and investment advisory at data firm TrackInsight, told the WSJ.

Vanguard has been the biggest winner this year, as its ETFs attracted almost $224 billion over the first seven months of 2021, or 45% more than all the money brought in so far in 2021 from BlackRock, the world’s largest ETF manager by assets.

The ETF industry is also gaining momentum in its actively managed category after asset managers got regulatory approval in 2019 to use stock-picking ETFs that also shield daily holdings, such as those provided by Fidelity Investments, T. Rowe Price, Putnam Investments, and others. These non-transparent ETF offerings are seen as adaptations to some of their mutual-fund strategies, with the ETF investment vehicle being cheaper and more accessible for investors.

While active ETFs still only represent a small slice of the overall ETF universe, the growing sector and increased interest among traditional fund providers could help drive further momentum in this ETF segment. Non-indexed ETFs, including those that actively pick stocks, held $358 billion in assets as of July, or about 4% of the overall ETF market, compared to $193 billion a year ago, according to Morningstar’s data.

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