Hmmm, that's an interesting question. I don't have anything in my library like that.
When I have to compile obscure labor statistics, I contact Jay Meisenheimer, with the Dept. of Labor, Labor Statistics. He's always been very helpful. His number is 202-606-6378.
This census may also have some information about this.
Rosada Bennett, Librarian
Federal Mine Safety and Health Review Commission
1730 K St., NW 6th Floor
Washington, DC 20006
(202) 653-5030 - fax