A rebound in growth and technology stocks has investors gauging whether a months-long rally in the shares of banks, energy companies and other economically sensitive names is running on empty or simply refueling.

The Russell 1000 value index started 2021 with its biggest quarterly outperformance relative to its growth counterpart in 20 years, as investors poured money into the shares of battered companies they thought would benefit most from a vaccine-generated reopening of the U.S. economy.

The script has flipped since mid-March, with the Russell growth index gaining over 6% compared to a rise of just over 2% for value. Some investors wonder whether the market has already priced in expectations of a powerful economic rebound on the stimulus, infrastructure spending and vaccine rollouts.

“We have already had a tremendous move” in value stocks, said Mona Mahajan, senior U.S. investment strategist at Allianz Global Investors. “We are probably at the stage where we just want to be a little bit more cautious, a little bit more selective.”

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