In the 2000 Census, respondents were able to indicate for the first time that they are multiracial. The latest figures from the 2010 Census suggest that the multiracial population is growing at higher than expected rates:

In the first comprehensive accounting of multiracial Americans since statistics were first collected about them in 2000, reporting from the 2010 census, made public in recent days, shows that the nation’s mixed-race population is growing far more quickly than many demographers had estimated, particularly in the South and parts of the Midwest. That conclusion is based on the bureau’s analysis of 42 states; the data from the remaining eight states will be released this week.

In North Carolina, the mixed-race population doubled. In Georgia, it expanded by more than 80 percent, and by nearly as much in Kentucky and Tennessee. In Indiana, Iowa and South Dakota, the multiracial population increased by about 70 percent.

“Anything over 50 percent is impressive,” said William H. Frey, a sociologist and demographer at the Brookings Institution…

Census officials were expecting a national multiracial growth rate of about 35 percent since 2000, when seven million people — 2.4 percent of the population — chose more than one race. Officials have not yet announced a national growth rate, but it seems sure to be closer to 50 percent.

This is interesting data, particularly since these figures exceed expectations. There are several issues to note with the data. First, some of the largest growth is taking places in states like Mississippi where there is a large percentage increase because there were so few interracial people in the 2000 Census. A second question we could ask about this data is whether this is primarily an increase in multiracial relationships or is it simply a reflection of changing measurements from the US Census? One sociologist suggests the second option could be plausible:

“The reality is that there has been a long history of black and white relationships — they just weren’t public,” said Prof. Matthew Snipp, a demographer in the sociology department at Stanford University. Speaking about the mixed-race offspring of some of those relationships, he added: “People have had an entire decade to think about this since it was first a choice in 2000. Some of these figures are not so much changes as corrections. In a sense, they’re rendering a more accurate portrait of their racial heritage that in the past would have been suppressed.”

So then perhaps we shouldn’t be surprised by these large increases in percentages; rather, we have better instruments by which to collect this data.

This Census data does seems to line up with changing attitudes about interracial relationships. In a recent story from Pew Research about what 90% of Americans can agree about, Pew showed how the approval of interracial relationships has grown a lot in the last several decades:

It is remarkable how this has jumped from 48% in 1987 to 83% approval in 2009. But if there is more approval for interracial relationships, then there is likely to be more relationships, marriages, and eventually children who identify as multiracial.