Until otherwise provided by law, the county treasurer shall remit to the county, school districts, cities, towns, other political subdivisions and the state of Arizona all sums received by him as voluntary contributions, in the same manner as property taxes are now distributed, and in amounts derived by reducing the gross contribution applicable to each such school district, county, city, town, other political subdivision and the state of Arizona to a sum equivalent to the proportion which the statewide net contribution bears to the statewide total gross contribution.