WASHINGTON – The nation’s minority population is steadily rising and now makes up 35 percent of the United States, advancing an unmistakable trend that could make minorities the new American majority by midcentury.

As white baby boomers age past their childbearing years, younger Hispanic parents are having children – and driving U.S. population growth.

“The aging of baby boomers beyond young middle age will have profound impacts on our labor force, housing market, schools and generational divisions on issues such as Social Security and Medicare,” said William H. Frey, a demographer at the Brookings Institution. “The engine of growth for the younger population in most states will be new minorities.”

New Census estimates show minorities added more than 2 percent in 2009 to 107.2 million people, boosted by a surge in Hispanic births and more people who described themselves as multiracial. During this time, the white population remained flat, making up roughly 199.9 million, or 65 percent, of the country.

By comparison, whites comprised 69 percent of the total population in 2000, and minorities 31 percent.

Currently four states – Hawaii, New Mexico, California and Texas – as well as the District of Columbia have minority populations that exceeded 50 percent. That’s one state more than in 2000, when Texas was not on the list.

About 311 of the 3,143 counties – one in 10 – have minority populations of 50 percent or greater. That’s up from around 250 counties in 2000.

The Census estimates released Thursday documented a widening age and race divide. They are the last government numbers before completion later this year of the 2010 census, which could change the balance of political power when legislative districts are redrawn based on population and racial diversity.