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What caused ETF flows to hit 16-month lows?

Getty Images. The Fed apparently can't find anything to reassure the markets with facts about the true state of the U.S. economy. So, here are some ideas.

Global exchange traded fund inflows slowed to a 16-month low in April, following the mixed messages from the U.S. Federal Reserve after its March meeting, as investors grapple with volatile data and sluggish global economic growth.

Flows into global exchange traded products (ETPs) -- securities that track an index, commodity or basket of assets -- eased to $6.5 billion in April, levels not seen since January 2014, where outflows of $6.7 billion were recorded.

Read More BlackRock Q1 earnings beat on strength of ETF flows

Flows are also sharply down from the money poured in since the start of the year, with March and February seeing $35.8 billion and $49.2 billion in inflows respectively.

"April was a weaker month for ETPs than March, but it continues to be a record year for the popularity of ETPs overall. More money has been put into ETPs so far this year than at the same stage at any other year in the industry's history," head of ETP research at BlackRock, Ursula Marchioni said.

Equity funds overall posted outflows for the month, led by redemptions in U.S. equity funds, which lost $15.5 billion of assets in April after the Fed sounded a cautious tone in its March meeting, causing stocks to rally.

BlackRock said fixed income flows benefitted following the meeting at the expense of equity funds, as investors worried of "stretched valuations" in stocks.

At its March meeting, the U.S. central bank dropped its pledge to be "patient" before raising interest rates, but it also sharply cut its projected path for interest rate increases, as growth and inflation forecasts remain weak.

While investors pulled money from U.S. stocks, European-based ETFs saw decent inflows, with over $5 billion flowing into pan-European equity funds, boosting European-based ETFs past the $500 billion mark for the first time.

"Some 60 percent of the market's growth in 2015 is down to European-domiciled funds. It's a great vote of confidence for the region in a month we celebrated its 15 year anniversary," Marchioni said.

Emerging market equity flows also picked up, seeing $2.5 billion of inflows in April, the "first notable inflows since August 2014", after the Fed cautious tone in March and April, according to BlackRock.

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