The challenges of high-skilled and low-skilled workers in the marketplace have been well-documented. But right now, it appears that many of the best opportunities may be in lesser-known "middle-skill" jobs.

These are the jobs that usually require more than a high school diploma but less than a four-year degree. Nearly three-fourths of U.S. companies expect increased demand for these workers in coming years, according to new research from Accenture. However, 56 percent of employers are having trouble filling these types of vacancies.

"The majority of U.S. employers across many business sectors are having great difficulty filling middle-skills positions, despite the fact that unemployment and under-employment remain a challenge for many Americans," said David Smith, senior managing director Accenture Strategy, Talent & Organization in New York City. "Our research provides employers with tangible and practical advice about how to address the underlying issues that contribute to the skills gap and how to improve their processes to source, develop, deploy and retain middle-skills talent."