Complex sentence: In the 2010 census, 2.9 million people self-identified as Native American, Native Hawaiian, and Alaska Native alone, and 5.2 million people identified as U.S. Native Americans, either alone or in combination with one or more ethnicity or other races.
Split into simpler sentences: In the 2010 census, 2.9 million people identified as Native American, Native Hawaiian, and Alaska Native alone. A total of 5.2 million people identified as U.S. Native Americans, either alone or in combination with one or more ethnicity or other races.