WASHINGTON  Demographers sifting through new population counts released on Thursday by the Census Bureau say the data bring a pattern into sharper focus: Young Americans are far less white than older generations, a shift that demographers say creates a culture gap with far-reaching political and social consequences.

Mississippi, Virginia, New Jersey and Louisiana all had declines in their populations of white residents ages 18 and under, according to the bureau’s first detailed report on the 2010 Census.

That drove declines in the overall white population for the decade in three of the four states. Only Virginia, whose northern suburbs have been growing fast, had a rise.

Growth in the number of white youths slowed sharply in the 1990s, up by just 1 percent in the decade, as the number of white women of childbearing age fell, according to Kenneth M. Johnson, a demographer at the University of New Hampshire.