Facebook Inc. employees are the youngest and most satisfied, and yet the most stressed, among workers at big U.S. technology companies, Bloomberg reported.

Facebook had the lowest median age, 26, as well as the highest proportion of female workers, 33 percent, among nine of the industry’s top businesses, according to PayScale Inc., a Seattle-based research firm. Employees at International Business Machines Corp. (IBM) and Hewlett-Packard Co. were the oldest surveyed, with a median age of 44.

The social-networking site, run by 27-year-old Mark Zuckerberg, has thrived by disrupting more-established technologies, such as Internet search and Web portals. That upstart spirit extends to its hiring policies, where workers aren’t judged by how many years they’ve spent in the business.

PayScale collected online surveys from employees at Amazon.com Inc., Apple Inc., Dell Inc., Facebook, Google Inc., Hewlett-Packard, IBM, Intel Corp. and Microsoft Corp. The results were not verified by the companies.

Apple’s median starting salary was $43,100, excluding employees from the company’s retail stores, according to PayScale’s survey. That puts it at the bottom on the list. Microsoft was highest, with initial pay of $86,900.

At Facebook, workers make about $59,100 to start, 49 percent more than the national average. They get a 13 percent premium over what employees would earn in similar positions at other companies, the survey found.