Employers still struggle to find new employees for technology-related occupations, sales, healthcare and a variety of other areas, according to research released today by CareerBuilder. More than a third of hiring managers — 35 percent — currently have positions that have remained open for 12 weeks or longer.

“Two in five employers (41 percent) reported that they continuously recruit throughout the year, so that they have candidates in their pipeline in case a position opens up down the road,” said Brent Rasmussen, president of CareerBuilder North America. “The skills gap that exists for high-growth, specialized occupations will become even more pronounced in the years to come, prompting the need to place a greater emphasis on reskilling workers through formal education and on-the-job training.”

Jobs cited as most difficult to fill, in order of jobs added from 2010 to 2013, include:

• Sales representative: 584,792 new jobs, 3.8 percent job growth 
• Machine operator/Assembler/Production worker: 135,363 new jobs, 9.9 percent growth
• Nurse: 135,325 new jobs, 5 percent growth 
• Truck driver: 113,517 new jobs, 6.7 percent growth 
• Software developer: 103,708 new jobs, 11.2 percent growth
• Engineer: 73,995 new jobs, 4.9 percent growth 
• Marketing professional: 57,045 new jobs, 11.3 percent growth
• Accountant: 55,670 new jobs, 4.5 percent growth
• Mechanic: 53,002 new jobs, 4.1 percent growth 
• IT manager/Network administrator: 48,709 new jobs, 7.5 percent growth 

The survey was conducted online within the U.S. by Harris Interactive on behalf of CareerBuilder among 2,046 hiring managers and human resource professionals between May 14 and June 5, 2013.