Apple Inc. surrendered the title of the world’s most valuable company to Exxon Mobil Corp. after concern over slowing growth drove the shares to the biggest loss in the Standard & Poor’s 500 Index.

Apple’s reign as the No. 1 stock ended after the shares slumped 17 percent this year, worse than any other companies in the benchmark gauge for U.S. equities. The decline reduced its market capitalization to $413.7 billion, below Exxon Mobil’s $416.5 billion.

The switch in rankings reflected fading confidence in Apple, whose 15 years of transformation from a near-bankrupt personal-computer maker to a technology leader dominating the smartphone and tablet market helped it become the most valuable U.S. company ever in 2012. Apple shares have fallen by 37 percent from a record in September amid concern that mounting costs and competition may curtail growth.

“You have one company that had pretty high expectations for it for the future and you have Exxon that continues to chip away slow and steady,” Jason Cooper, who helps oversee $2.5 billion in South Bend, Indiana, at 1st Source Investment Advisors, said in a phone interview. His firm owns both Apple and Exxon shares. “People are coming to the realization that Apple is losing a little bit of floss and shine.”