Robert D’Alelio has the kind of long-term record every mutual fund manager aspires to, beating 98 percent of his peers over the past 15 years with the $12.6 billion Neuberger Berman Genesis Fund and crushing his benchmark, the Russell 2000 Index.

D’Alelio’s performance over the past five years isn’t so enviable. He’s fallen behind his yardstick, and he’s got lots of company. Stock pickers including Donald Yacktman at the AMG Yacktman Fund and the team of O. Mason Hawkins and G. Staley Cates at the Longleaf Partners Fund trailed their barometers in the same period after dominating in the prior decade.

Managers say they haven’t changed, the market has. The easy money climate of near-zero interest rates engineered by the Federal Reserve has artificially inflated prices of lower-quality U.S. stocks, they say, punishing those who focus on businesses with the best fundamentals. At the same time, the relentless climb of prices across equity markets has left them with few chances to sniff out bargains or show what they can do in more-volatile times.

“In straight-up markets you don’t need active managers,” D’Alelio said in a telephone interview. “If the next five years are the same, there won’t be any active managers left.”

Twenty percent of mutual funds that pick U.S. stocks beat their main benchmarks in 2014, and 21 percent topped the indexes in the five years ended Dec. 31, according to data from Chicago- based Morningstar Inc. Over 10 and 15 years, the winners rise to 34 percent and 58 percent, respectively.

Fund Redemptions

Investors have expressed their displeasure by moving money to low-cost funds that mimic indexes. In 2014, actively run U.S. stock funds suffered $98 billion in redemptions, while index funds took in $167 billion. Passive managers represent 38 percent of the $8.7 trillion stock fund business, more than twice their share 10 years earlier, Morningstar data show.

The shift may be ill-timed if the herd mentality comes to an end. Lagging behind the market will motivate managers to change their investment process and common sense will prevail as the economic cycle ages and fundamentals are rewarded, Brian Belski, chief investment strategist at BMO Capital Markets, wrote in the firm’s 2015 outlook published in December.

“From our lens, this means a prolonged period of active investing is upon us, thereby overtaking the macro or index biased ways that have engulfed investing the past 15 years,” Belski wrote.

Royce Funds, the small-cap stock unit of Baltimore-based Legg Mason Inc., is undeterred after more than $17 billion in redemptions during the past four years. The $4.9 billion Royce Premier Fund beat 97 percent of rivals over 15 years, a number that drops to 7 percent over five years, Morningstar data show.