From Ohio History Central
In 1972, the Ohio state government implemented an income tax. This tax was a progressive one. Under a progressive income tax, the people who earn the most money pay a higher percentage of their income in taxes.
Ohio implemented this income tax for numerous reasons, chief among them being the need for additional funds to finance state projects. Some of the money generated by the income tax went to education. The personal income tax also allowed the state government to reduce taxes on businesses. During the late 1960s and early 1970s, many businesses were leaving Ohio. Ohio officials hoped to reverse this trend by reducing the tax burden on businesses. Unfortunately for Ohio residents, the state needed to find a new source for money lost by the business tax reductions. Thus, the income tax began.