J.C.K. or Jewelers Circular Keystone Magazine publishes various data
related to the industry,, sales by category/region/#of employes
etc... or perhaps the J.B.T. Jewelers board of trade,,, (a jewelers
credit rating company) can help,,, also the most helpfull may be to
call the GIA (Gemological Institute of America, Carlsbad CA) ask the
librarian and they can deffinetly help you ....