SAN FRANCISCO (MarketWatch) -- Upward revisions to earnings estimates for the S&P 500 SPX, +0.82% have been overly optimistic, said Adam Parker, chief investment strategist at BernsteinResearch, in a report Tuesday. Consensus estimates for 2010 imply 30% growth in earnings per share to $82 a share in 2010, and 18% growth to $97 a share in 2011. In contrast, Parker predicts 25% EPS growth for 2010, to $79 a share, and 9% growth in 2011 to $86 a share. "Our view is that the EPS estimates embedded in consensus are too high for 2011 and perhaps for the second half of this year," wrote Parker. The "record pace" of upward revisions has fueled too much optimism, he said. "The challenge is that you will likely not see any evidence of this in the first half of the year," he said. He recommended owning companies with lower EPS growth expectations.