Mich. Comp. Laws § 397.32
The proceeds of all fines for any breach of the penal laws of this state when collected in any county and paid into the county treasury, together with all moneys heretofore collected and paid into the county treasury on account of such fines and not already apportioned, shall be apportioned by the county treasurer in accordance with the directions of the state board for libraries, as provided in section 8, before August 1 of each year among those public libraries and county libraries established under Act No. 138 of the Public Acts of 1917, as amended, being sections 397.301 to 397.305 of the Compiled Laws of 1948, or Act No. 250 of the Public Acts of 1931, as amended, being sections 397.151 to 397.158 of the Compiled Laws of 1948, or county library boards in each county entitled to such fines under this act on a per capita basis determined by the population of the governmental unit supporting the library according to the latest decennial or special federal census.
MCL 397.32