Nearly 10 million Americans reported belonging to different race or ethnicity during census surveys in 2000 and 2010, according to a new study at the University of Minnesota and the Census Bureau.

The researchers said that citizens swapped between races, moved from multiple races to a single race vice-versa or decided to add or drop Hispanic ethnicity on census forms. The reasons as to why people made these changes have not been determined in the study.

"Compared to adults, children and adolescents may be more likely to change their race/Hispanic responses for two reasons: childhood and adolescence are times of personal identity development and young people's information was probably reported by their parents in 2000 but may be self-reported in 2010," researchers said in a statement.

The researchers said that one in 16 people - or approximately 9.8 million (8.3 percent) of 162 million - who were part of both the 2000 and 2010 censuses responded differently to questions of race and ethnicity.

The largest change was observed among Hispanic populations, where around 2.3 million people changed from Hispanic (some other race) to Hispanic white. On the other hand, 12 million people changed from Hispanic white to Hispanic (some other race). Combined together, the two changes constituted more than a third - 37 percent - of the race/ethnicity modifications in the report, News Observer reports.

The second biggest change also had a similar effect. About 710,019 people decided to change from white to Hispanic white, and 417,855 moved from Hispanic white to white within that time frame from the 2000 to the 2010 census.

The study also found that the changes were mostly made by children and/or living in the West in 2000 because this region experienced higher rates of interracial marriages. The census defines the West as Alaska, Arizona, California, Colorado, Hawaii, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington and Wyoming.

The most stable groups were single-race, non-Hispanic whites, blacks and Asians, who checked same boxes in both censuses.

Tags Americans, Minnesota, Race