That's helped drive equities' rotation into the more defensive, high-dividend paying names, also typically part of the low-beta camp.
So far this year, the 50 stocks in the S&P 500 .SPX with the lowest beta scores - a group that includes ConEd and McDonald's - are up on average by 12 percent. Meanwhile, the 50 highest beta stocks, which include Citigroup and Best Buy, are up an average of 7 percent.
In 2013, the 50 highest-beta S&P 500 stocks rose an average of 51.4 percent, compared with 21.3 percent for the 50 lowest-beta stocks.
Investors who have pursued the high-beta contingent have suffered. Among them are hedge funds, which kept a heavy exposure to momentum-type names and the "beta" strategy.
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Hedge funds now have 3.8 times more net cyclical exposure to defensive stocks, said Jon Kinderlerer, a managing director at Credit Suisse. In January, that measure was 4.7 times - bets that went sour as the market corrected through the first quarter.
"Once that trade began to break, that also accelerated a rotation back into more value-oriented names and sectors," said Mark Luschini, chief investment strategist at Janney Montgomery Scott in Philadelphia.
Bigger dividends, higher valuations
This year's winners deliver nearly twice the dividend yield than their high-beta counterparts. Stocks with the lowest betas have an average dividend yield of 3.1 percent compared with 1.7 percent for high-beta stocks, Thomson Reuters data shows.
What's unusual is that S&P's high-beta stocks are at some of their cheapest valuations ever relative to the S&P 500, said Bernstein, whose data goes back to 1986.
To Bernstein, that's a positive sign for the market's long-term health as it shows investors aren't overpaying for growth. "Find me a market peak where investors have been scared of beta," he said.
He noted, however, that there are plenty of high-beta names among the broader stock universe like the Russell 2000 with rich valuations - companies like Monster Worldwide - which aren't in the S&P 500.
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Among stocks with the highest betas in the S&P 500, Seagate Technology has a P/E of just 10.6, while Hartford Financial Services Group has a P/E of 10.9.
The high beta stocks currently have a median P/E of 15.2 versus a median P/E of 16.4 for all of the S&P 500 stocks with beta scores. The low beta names have a median P/E of 16.1.
Growth sectors have rebounded in recent sessions as the earnings outlook has improved, with calendar year 2014 estimates rising to 9.1 percent as of June 6 from 8.7 percent on April 1, according to Thomson Reuters data.
"Everything is hanging on the estimates for growth in the second half. How that plays out will determine whether higher beta or low beta outperform for the year," said Bucky Hellwig, senior vice president at BB&T Wealth Management in Birmingham, Alabama.