From Bowker's, I have been able to find out how many history and
science non-fiction books are produced each year by the publishing
industry. I need to know the corresponding sales estimates (#'s
shifted, overall revenue generated) for these two categories over the
past couple of years in the U.S. When Bowker does provide sales charts
for the publishing industry, unfortunately it does not provide this
kind of detail; it only provides sales figures for hardcover,
paperback, religious, etc. I am hoping that you can provide this data
from other sources.

If possible, I would prefer sales estimates that cover bookstores,
book clubs, online retailers, etc., but would take whatever numbers
reasonably cover the most terrain.