In July, Morningstar reported that actively managed mutual funds suffered their worst 12-year period of outflows ever.

U.S focused funds saw $156 billion flow out in that period, while passively managed funds that tracked the S&P 500, Nasdaq, and Russell 1000 indices gained $150 billion of inflows.

The exodus continued in August: $14 billion flowed out of actively managed U.S. equity funds, while $5 billion flowed into index funds.

In spite of the continued hemorrhaging, a new study from American Funds suggests retirement investors can vastly extend the life of their savings with actively managed funds, so long as the right funds are chosen.

The study cites what it calls three critical factors in assessing the value proposition of actively managed funds:

• low expense ratios

• a high level of investment in the funds by its managers

• whether or not the funds outperformed indexes during market downturns

The study compared two hypothetical portfolios of actively managed funds that met the three critical factors with portfolios built on passively managed index funds.

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A 65-year old investor retiring in 1995 with $500,000 in savings who began withdrawing 4 percent, and increased annual withdrawal by 3 percent each year after to account for inflation, would have generated 85 percent more wealth in one active model compared to an investor in a passively managed portfolio, according to the study.

In one scenario, the investor would have been able to withdraw $537,000 by year-end 2014—a 20-year period—and still have $1.7 million remaining in the actively managed account.

If invested in a passive index blend of comparable equities, the investor would only have about $908,000 in wealth after drawing down $537,000 in assets over the 20-year period.

Independent research from Morningstar shows the least expensive actively managed funds often performed well in the past year.

Large-cap actively managed funds with expense ratios below 30 basis points beat the market 56 percent of the time, while funds with expense ratios greater than 50 basis points only outperformed markets 40 percent of the time.

Morningstar’s research also shows that actively managed funds that invest in their own strategies also outperform those funds that don’t invest their own money.

“The right actively managed funds can be a strong value-add to many 401K portfolios and some, including those from American Funds, have fees lower than many passively managed funds,” said Steve Deschenes, head of client analytics at Capital Group, which owns American Funds, in an email interview.

“It’s important to consider that passive funds will bear all the downside of a market downturn which can be a serious setback for those saving for or nearing retirement,” he added.

“Our new study shows that selecting actively managed funds with a low expense ratio, high manager ownership and a low downside capture have historically outpaced indexes and active peers in a withdrawal scenario. We encourage advisers to weigh this information when making recommendations to companies and platforms of a good mix of 401K options for plan participants,” said Deschenes.