NEW YORK (AP) — Walmart CEO Doug McMillon, who turned America’s largest retailer into a tech-powered giant and spearheaded a period of robust sales growth since becoming chief executive in 2014, plans to retire early next year, the company said Friday in a surprise announcement.

John Furner, 51, the head of Walmart’s U.S. operations, will take over on Feb. 1, the day after McMillon’s retirement becomes effective, the company said. Although McMillon is set to spend a year advising his successor, Walmart shares fell 3% immediately in premarket trading after the news of the unexpected leadership change but recovered somewhat and were down 1% by midday trading.

Unlike Amazon’s Jeff Bezos or Tesla’s Elon Musk, McMillon isn’t a household name, but he has played a key role in the U.S. economy. Walmart’s performance serves as a barometer of consumer spending given its size and vast customer base. The company maintains that 90% of U.S. households rely on Walmart for a range of products, and more than 150 million customers shop on its website or in its stores every week.

Walmart, based in Bentonville, Arkansas, also is the nation’s largest private employer, with 1.6 million workers. That includes corporate personnel and people working for Sam’s Club, the membership warehouse-store chain that Walmart owns. Globally, Walmart employs 2.1 million people.

The pending CEO switch comes at a challenging time for retail companies and other employers that have spent almost 11 months navigating an uncertain economic environment as President Donald Trump’s administration imposed wide-ranging tariffs on imports and initiated an immigration crackdown that threatened to shrink the supply of workers.

McMillon, a University of Arkansas graduate, started with Walmart in 1984 and became chief executive three decades later. During his tenure as CEO, he invested heavily in employees by increasing wages, expanding parental leave and launching a program for employees seeking advancement and education opportunities to earn certificates and degrees.

Under his leadership, Walmart has been laser-focused on maintaining low prices while embracing new technology like artificial intelligence and robotics. McMillon also helped to improve the company’s reputation, softening its image as a ruthless low-price operator by personally connecting with hourly workers and committing to goals such as reducing the carbon emissions that cause climate change.

“Over more than a decade as CEO, Doug led a comprehensive transformation by investing in our associates, advancing our digital and e-commerce capabilities, and modernizing our supply chain,” Walmart Chairman Greg Penner, the son-in-law of the late Walmart founder Sam Walton, said. “He leaves Walmart stronger, more innovative, and better aligned with our purpose to help people save money and live better.”

Furner started at Walmart in 1993, working as an hourly store associate in Bentonville. He has lived and worked in multiple countries, and served as president and CEO of the U.S. division of Sam’s Club before taking the same roles at Walmart U.S.

TD Cowen analyst Oliver Chen wrote in a report published Friday that Furner has “robust experience” refining Walmart’s U.S. business. Chen expected the new CEO to maintain company’s overall strategies but said that “a Doug McMillon chapter won’t be easy to follow. ”

“McMillon was not only a visionary but also a humble person, who connected with people extraordinarily well,” Chen said.

Walmart’s annual revenue jumped 40% under McMillon, from $485.7 billion at the end of the first fiscal year with him as CEO to $681 billion in its latest fiscal year. Its stock was hovering around $25 per share when he came to the helm; now, it’s over $102.

McMillon took over as CEO from Mike Duke, who spent six years leading the company following the unexpected retirement of chief executive Lee Scott — also at age 59.