The lack of new highs in the past year mimics the performance of previous bull markets before they took off, according to research by Bank of America Merrill Lynch.
"Investors hate to chase a rally, but a new high after a long pause would be a bullish signal," technical research analyst Stephen Suttmeier wrote in a recent note to clients.
Since reaching a record price of 2,134.72 on May 20 last year, the S&P benchmark has gone through a period of volatility, failing to reach a new high as investors debate the longevity of the bull run, now the longest on record.