As the number of young Hispanics born in this country has grown over the past 14 years, so too their proficiency in English as fewer said they speak Spanish at home, according to a new study released Wednesday by the Pew Research Center.

The study is based on an analysis of 2014 U.S. Census Bureau data. It finds 65 percent of Hispanics in 2014 were U.S. born, compared with 60% in 2000. Also, one-third, or 17.9 million, of the Latino population is younger than 18 years old. Of these, 88 percent said they speak only English at home or speak English very well. In 2000, only 73 percent said the same.

That trend is also evident among the 14.6 million Latino millennials, ages 18 to 33. Among this cohort, 76 percent said they speak only English at home or speak English very well. That's up from 59 percent in 2000.

It all follows from the fact that U.S. births are the main driver of Hispanic population growth, said Mark Hugo Lopez, director of Hispanic research at the Pew Center.

"Immigration into the United States has slowed substantially in the last ten years and that's lead to the English proficiency rise among Hispanics," he said. "A greater share of Hispanics today prefer to get their news in English than was the case just ten years ago."

Still, attitudes about language among are complex, says Lopez. In a past survey, the vast majority of Hispanic adults said it is important for future generations of Latinos to speak Spanish.

"But we've also asked Hispanic adults 'do you need to speak Spanish to be considered Hispanic?' And interestingly, seven in ten Hispanic adults tell us, 'no, you don't need to speak Spanish to be considered Latino.'"

The growing number of under-18 U.S.-born Hispanics will have a major impact on the country's political system too. "Every year about 800,000 young Hispanics, most of them U.S.-born, turn 18," said Lopez.

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