(NaturalNews) As many as half of workers in the United States may be trapped in jobs that they would like to leave, out of fear of losing their health insurance. Experts say that this phenomenon, known as "job lock," is not only making people unhappier, but also stifling the innovation that could emerge if more people were able to freelance or work for smaller companies."We can definitely say that it's slowing down the rate of innovation," said economist Tim Kane of the Kauffman Foundation.The most common source of health insurance in the United States is private insurance purchased at least in part by an employer. The costs of private insurance mean that many small companies, unable to qualify for the bulk discounts that the big companies command, simply cannot afford to offer their employees insurance. The situation is even more dire for self-employed workers, who are responsible for the full cost of their insurance."I would rather be freelancing, no question," said public relations professional Jessica Tolliver. "I got my work done in less time, because once I finished what I had to do, the time was my own."When Tolliver was a freelancer, however, the insurance costs for her family ran an astonishing $1,200 per month. As an employee, she pays only $200 per month.An estimated 20 to 50 percent of all workers in the United States are trapped in job lock due to health insurance fears. The significance of this number is brought home by the fact that only 60 percent of the U.S. population has work-based health insurance -- meaning that for between 33 and 83 percent of workers with job-based health coverage, this insurance is the only thing keeping them in their jobs.While President Barack Obama has promised an overhaul of the U.S. health care system , the problem of job lock is likely to remain. Private health insurance remains the foundation of Obama's reforms.Sources for this story include: www.reuters.com