A third of Americans say they have gone without medical care or skipped filling a prescription because of cost, compared to 5 percent in the Netherlands, according to a study released on Thursday.

The study published in the journal Health Affairs is the latest in a series by the non-profit Commonwealth Fund showing that while Americans pay far more per capita for health care, they are unhappier with the results and less healthy than people in other rich countries.

“U.S. adults were the most likely to incur high medical expenses, even when insured, and to spend time on insurance paperwork and disputes or to have payments denied,” the report reads.

The Commonwealth Fund, which advocates for U.S. health care reform, commissioned a Harris Interactive poll of nearly 20,000 people in 11 countries between March and June.

“What we are hearing directly from adults around the world, and what we hear regularly at home, is that there is substantial room for improvement in the U.S. health insurance system,” said Commonwealth Fund President Karen Davis.

Health care reform was U.S. President Barack Obama’s signature policy effort, but not a single Republican voted for the bill that Obama signed into law this year. Conservatives in Congress have promised to try to dismantle it.