The county librarian shall, on or before August 31st, in each year, report to the board of supervisors and to the State Librarian on the condition of the county free library, for the year ending June 30th preceding. The reports shall, in addition to other matters deemed expedient by the county librarian, contain such statistical and other information as is deemed desirable by the State Librarian. For this purpose the State Librarian may send to the several county librarians instructions or question blanks so as to obtain the material for a comparative study of library conditions in the state.