Morgan Stanley's U.S. chief equity strategist, Adam Parker, has been bullish for several years, but he told CNBC on Wednesday he's now getting more cautious.
While he's not bearish, he said the change in the investing landscape has led to a "big inflection point in my thinking."
Morgan Stanley's bullish thesis was built around the view that earnings growth was low but the price-to-earnings ratio, or multiple, would expand. Now, earnings are expected to grow but the P/E ratio will likely start to contract and begin to offset that earnings growth, Parker explained.
"So I think this year is a bit of the tension of higher earnings, lower multiples, and that's a new regime."
Lower ratios are typically associated with companies that have low growth.