Though relatively high unemployment persists in the United States, employers are not having an easy time hiring workers for jobs they deem critical, according to the sixth annual talent shortage survey from Manpower Inc., a staffing agency.

In a survey of 1,300 U.S. employers, the results of which were released in May 2011, 52% of respondents said they were experiencing difficulty in filling “mission-critical” positions. That’s up from 14% for the 2010 survey. And, according to Manpower, U.S. employers are having a tougher time filling such jobs than employers outside the United States.

"The fact that companies cite a lack of skills or experience as a reason for talent shortages should be a wake-up call for employers, academia, government and individuals," says Jonas Prising, ManpowerGroup president of the Americas. “There may also be an increasing imbalance between employer willingness to pay higher salaries in what is still a soft general labor market compared to the salary expectations of prospective employees, especially those with skills that are in high demand."

Among the jobs that have become the hardest to fill in 2011 are sales representatives, the No. 2 most difficult position to fill; engineers, No. 3; information technology staff, No. 6; and management and executive positions, No. 7.

In fact, the information technology sector added 100,000 jobs in May, according to Janco Associates Inc., a management consulting firm that focuses on information technology, and which bases its projections on data from the U.S. Bureau of Labor & Statistics. The largest gain in May was in I.T. support functions, which tend to be lower-paying jobs than others in the industry.  Janco attributes this particular boost to companies beginning to rehire for staff positions that were the first to be cut during the recession.

“There definitely are some positive signs in the I.T. employment market,” says Janco CEO Victor Janulaitis. “Companies are starting to fill positions that are open in support functions and where there are critical needs.”

Beyond I.T., e-commerce seems especially in need of qualified workers, at least judging by comments made by speakers at the Internet Retailer Conference & Exhibition 2011, held in San Diego in June. Retailers small and large urged audience members to pass along any qualified candidates for a variety of jobs, including technical ones. Web-only retailer Newegg.com, in fact, said it had dozens of openings.