Mr. Trump, meanwhile, has emphasized the importance of boosting U.S. jobs, a subject that could put tech firms on the defensive. Apple, Alphabet, Microsoft, Amazon and Facebook are five of the seven most valuable companies in the U.S., yet they generally employ fewer people than big firms in other industries. The five together employ about 600,000 people, many of whom work abroad. Wal-Mart Stores Inc., meanwhile, employs 1.5 million in the U.S. The tech industry’s heavy reliance on software limits the need for as many employees as other industries to manufacture, sell and distribute products and services.