Mr. Pertman, director of the Evan B. Donaldson Adoption Institute, estimates that the number of US adoptions from abroad has tripled in the past decade.
"When you look at the number of people adopting from Asia, from Latin America - more than half are adopting from countries where the kids aren't going to look anything like their parents," he says. "That's starting to make a difference in the way people think of families, of inheritance, of nurture versus nature, you name it."
More people are marrying people who don't look anything like them, as well. But Mr. Frey, who analyzed detailed microsamples of census data, found that the numbers varied highly from state to state. In New Mexico, for instance, 16 percent of all marriages were interracial, whereas in Mississippi it's 2 percent.
"There are two ways of looking at this," Frey says. "One is, it's gone real fast. And two: It's pretty concentrated in just a few states.... It's still a pretty small share of all marriages, especially those involving whites."
It's worth noting that unlike most census analysts, Frey treated Latinos as a racial group, and nearly half of the 3.7 million interracial marriages he counts include a Latino.
Frey calls some of the states with the highest percentages of mixed-race marriages - such as New Mexico, California, and Hawaii - "melting pot" states: All have several significant minority groups, not just one.
That's something Brigitte Ball can attest to. A corporate librarian in Boston, Ms. Ball has been married for two years. She is African-American; her husband, Jeff, is white. They met in Seattle, Brigitte's hometown. There, she says, she grew up with far less segregation by neighborhood than she sees in cities like Boston. Her best friends include women who are biracial, Jewish, and Latina.
"We're like a United Nations bunch," she laughs.