Among U.S. technology companies with market values exceeding $100 million, almost 50 increased employment by more than half in the most recently reported two-year period, according to data compiled by Bloomberg.

Some small and mid-size businesses boosted payrolls almost fivefold, underscoring the resilient demand for Internet services, software and electronics.

In the software and services industry, 74 companies with more than $100 million in market value expanded their work force by at least 10 percent. That was more than any other industry group measured by Bloomberg.

Apple Inc., Google Inc. and Amazon.com Inc. were among the companies that increased their work force by at least 50 percent in the past two years, Bloomberg’s data showed.

Apple, which started with a large employee base, grew 76 percent. That amounted to 26,100 new jobs.

The appetite for employees isn’t showing signs of waning. Amazon and Facebook Inc. each plan to add thousands of jobs in 2012, many in new satellite offices. EBay Inc. and Tibco Software Inc. also are stepping up their recruiting.

Some employers are concerned that the hiring spree resembles the go-go days of the dot-com bubble. When technology stocks crashed in 2000, thousands of jobs vanished. Silicon Valley lost more than 85,000 positions between 2001 and 2008, and other technology hotbeds suffered similar losses.