The number of American adults with mixed-race backgrounds is three times what official census figures indicate, and the figure is rising fast, according to a survey released Thursday. But most do not call themselves multiracial.

The Pew Research Center survey found that 6.9 percent of adults in the United States were multiracial, based on how they identify themselves or on having parents or grandparents of different races. By comparison, the 2010 census reported 2.1 percent of adults, and 2.9 percent of people any age, as multiracial, based on people’s descriptions of themselves or others in their households. (Hispanics are considered an ethnic group, not a race.)

By any measure, the multiracial population is tracing a steep upward curve, with children being more than twice as likely as adults to meet Pew’s definition. The Census Bureau, which first allowed people to identify with more than one race in 2000, estimates that the number of people doing so will triple by 2060.

Interracial sex and marriage was outlawed in many states until 1967, when the Supreme Court struck down those prohibitions in Loving v. Virginia. Today, the United States is increasingly not only a multiracial country, but also a country of multiracial individuals, including the first biracial president, living in an era of rising acceptance and visibility.