At the close of each year the board of trustees of every library shall make a report to the legislative body of the governmental unit wherein the board serves, showing the condition of their trust during the year, the sums of money received for the library fund from taxes and other sources, the sums of money expended and the purposes of the expenditures, the number of books and periodicals on hand, the number added during the year, the number retired, the number loaned out, and such other statistics and information and such suggestions as they deem of public interest. A copy of this report shall be filed with the state librarian.