(Reuters)—The percentage of Americans who have health insurance through their employer slipped to a new low of 44.5% in the third quarter, a drop of more than 5 percentage points in three years, according to a new poll released Friday.

Pollsters at Gallup and Healthways Inc., who surveyed more than 90,000 U.S. adults, blamed the decline on high unemployment, under-employment and an increased number of employers who do not offer health insurance to their workers.

Employer-sponsored health insurance is one of the main pillars of the $2.6 trillion U.S. health care industry. But companies have increasingly scaled back benefits and raised employee charges to cope with health care costs that are rising sharply despite anemic economic growth.

The latest figure was 5.3 percentage points below a high of 49.8% in 2008, when the two companies began tracking trends in employer-sponsored health insurance.

"The health insurance system in the United States is experiencing numerous changes. Governments and businesses have and will continue to cut back and/or reform their health coverage offerings," the pollsters said in a statement.

Retailing giant Wal-Mart Stores Inc. announced in October that it would no longer offer health insurance to new part-time employees and slashed its contributions to employee health expense accounts.

As employer-sponsored insurance declined, the number of adults with no health insurance at all rose 2.7 percentage points to 17.3% in the third quarter.

There was also an increase in the ranks of those covered by government plans from Medicaid, Medicare and military programs, which was up 2.2 percentage points since 2008 at 25.1% but off a 2010 high of 25.7%.

According to the Kaiser Family Foundation, there were 41 million uninsured American adults and 24 million adults on Medicaid and other public insurance plans in 2010.

The survey found higher health insurance coverage among young people aged 18 to 26, which pollsters attributed to a provision of the U.S. health care overhaul that allows parents to cover grown children under their insurance plans.

But other segments of the law, including tax credits for small businesses, did not appear to be help older adults, aged 25 to 64, whose uninsured ranks increased.

Conducted July 1 to Sept. 30, the survey has a 1 percentage point margin of error.