WASHINGTON (Reuters) – The number of uninsured U.S. young adults, who already represent a major chunk of the American population without health coverage, rose again in 2006, according to a study released on Friday.

Based on census data, 13.7 million people aged 19 to 29 had no health insurance, either public or private, in 2006, up from 13.3 million in 2005, according to a report by the Commonwealth Fund, a private foundation that researches health policy.

Men and women in this age group accounted for 17 percent of the under-65 U.S. population, but made up almost 30 percent of the uninsured, according to the report. At age 65, people enter the federal Medicare insurance program.

“There has been a steady upward climb in the number of young adults without health insurance coverage,” Sara Collins, an author of the report, said in a telephone interview.

Reducing the number of Americans who lack health insurance has emerged as an issue in this year’s U.S. presidential campaign. The government estimates that 47 million people have no health coverage in a country of about 300 million.

“If you ask young adults, as we do in our survey, if you’ve ever had problems accessing health care because of cost — not filling a prescription, not seeing a specialist — two thirds of uninsured young adults say yes,” Collins said.

Hispanic and black young adults were at greater risk of being uninsured than whites, the report showed. While 23 percent of whites ages 19 to 29 lacked insurance, the figure was 36 percent of blacks and 53 percent of Hispanics.

Those aged 19 to 29 represent one of the largest and fastest-growing segments of the U.S. population lacking health insurance, the report said.

The U.S. uninsured rate rises dramatically at age 19 — from 12 percent of children up to age 18 up to 30 percent among men and women aged 19 to 29, according to the report.

They often are dropped from public insurance programs at 19 or from parents’ private insurance policies once they finish their education, either graduating high school or college.

Many jobs available to young adults tend to be low-wage or temporary, the type often unlikely to provide health coverage.

The report showed that 38 percent of high school graduates who do not attend college and 34 percent of college graduates spend some time uninsured in the year after graduation.

(Editing by Maggie Fox and Eric Walsh)