Many analysts say that the rapid growth in U.S. corporate earnings may have peaked in the first quarter of this year, according to a recent article in The Wall Street Journal.

According to FactSet data, the article says, earnings growth is expected to reach 19% in the second quarter, 21% in the third and 17% in the fourth, with numbers in the single digits next year. But some analysts argue that the slowing might be a result of the one-time boost from the federal tax overhaul and that growth could remain high as the economy continues to reflect “renewed signs of strength and consumer and small-business confidence riding high.”

That said, the article argues that the nine-year bull market run has produced stock prices that reflect a “rosy outlook that is already showing signs of fading on a number of fronts,” including disappointing global growth, further planned rate hikes by the Fed and the threat of trade war.

Mark Haefele, chief investment officer at UBS Global Wealth Management, was quoted: “We’re at an interesting inflection point where we’re moving later into the cycle. Whether earnings roll over is going to be the deciding factor that ends this cycle.”

According to Titus Wealth Management managing director Scot Lance, companies would have grown first-quarter earnings by only single digits if not for last year’s tax cuts. He said however, that it would “still support further stock gains, because companies have also been growing their revenues, a sign that recent gains haven’t just come from cost-cutting.”

But as earnings growth slows down, the article concludes, stocks will look more expensive. “That is something investors say could make it more difficult for the stock market to keep rallying.”