The Cooperative Children's Book Center (CCBC) at the University of Wisconsin-Madison publishes CCBC Choices each year. It includes statistical data about numbers of books written by authors of color.
The information I share below is from "Thoughts on Publishing in 2008" by Kathleen T. Horning, Merri V. Lindgren, Tessa Michaelson, and Megan Schliesman. It was originally published in CCBC Choices 2009. I encourage you to become a Friend of the CCBC, which includes a copy of Choices.
In 2008, CCBC received 40 books that featured American Indian themes, topics, or characters. Of those 40, nine were created by American Indian authors and/or illustrators.
Here's two paragraphs from the essay, in the section titled "Multicultural Writing (and Illustrating, Too!)":
Louise Erdrich continued her chronicle of nineteenth-century American Indian experience in The Porcupine Year, which picks up the story of the Ojibwe girl Omakayas, last seen in The Game of Silence (HarperCollins , 2005). Now forced to leave their home, Omakayas’s family is on the move in a story based in part on Erdrich’s own family history.Joseph Bruchac, the most prolific Native author for children and teens, was inspired by family history to research and write what became March Toward the Thunder, about an Abenaki boy serving in the Union army during the Civil War. Update on Sep 30 2023: I (Debbie Reese) no longer recommend Bruchac's work. For details see Is Joseph Bruchac truly Abenaki? Nicola Campbell’s picture book Shin-chi’s Canoe looks at Native boarding schools through the a story of a boy enduring his first year away from home.
Horning, Lindgren, Michaelson and Schliesman note that few new picture books that show contemporary children of color were published. They write:
In fact, the only 2008 picture book featuring a contemporary American Indian child that we documented here at the CCBC was Niwechihaw=I Help, a bilingual (Cree/English) book published by Groundwood Books / House of Anansi Press. The Littlest Sled Dog (Orca) features a dog rather than a child or children but does offer a glimpse of a contemporary Inuit village. And The Drum Calls Softly (Red Deer Press) is a bilingual (Cree/English) picture book in the voice of a child who might be contemporary or from the past, although the stunning illustrations by Native artist Jim Poitras (Cree, Salteaux, and Métis) have a historical sensibility.
On October 24, 2008, I posted a table of data from CCBC specific to books by and about American Indians. It covered 2002 through 2007. I'm reposting that table here, adding 2008 statistics to the table.
Year---Number of bks---About Amer Ind---By Native writer
2002--------3,150--------------------64-----------------------6---------------
2003--------3,200--------------------95----------------------11--------------
2004--------2,800--------------------33-----------------------7--------------
2005--------2,800--------------------34-----------------------4--------------
2006--------3,000--------------------41----------------------14-------------
2007--------3,000--------------------44-----------------------6--------------
2008--------3,000---------------------40----------------------9--------------