A year that began on a dark note for stock investors has finally started to brighten. As U.S. markets continue a slow climb from a February trough, capital is flowing back into funds that invest in American stocks. 

In the week ended Wednesday, $4.6 billion flowed into U.S. stock funds, snapping a nine-week stretch of cumulative outflows. For the first time in 2016, more investors wanted into stock-based mutual funds and exchange-traded funds than wanted out, data from Lipper showed. 

Stocks have been on a steady upswing since hitting a floor on Feb. 11, when the Standard & Poor's 500-stock index ended down 13 percent from its most recent peak in early December. In the weeks since, the S&P 500 has added back 180 points, or 9.8 percent, opening Friday at 1994.71.

But trepidation remains, especially as Europe, China and emerging markets continue sending lackluster economic signals. "This rally looks like a head fake to me, a manufactured upswing that will lure many unwary investors into further investment in a dangerous market," Dawn Bennett, CEO of Bennett Financial Services, wrote in a recent note to clients. 

But even as investors pile back in, mutual funds have posted middling results this year. As Goldman Sachs analysts led by David Kostin pointed out in a note Friday, large-cap mutual funds have been overweight in sectors that have slid furthest in the first few months of the year, such as bank stocks, while investing less in sectors that have outperformed, namely telecoms. 

So far this year, investors have pulled a net $6.6 billion out of large-cap mutual funds, Goldman said.