There have been four major trends in state taxation over the years, and can be seen in North Carolina's tax system as well. First, the distribution of tax impact has show a ratio of total support in favor of steady relief of property tax. This was followed by the progressive versus proportional taxation, where the state has had only two opportunities to introduce progressive tax structures--personal income tax, and estate and inheritance tax. The third trend was the development of local non-property taxes due to pressure on property tax following World War II, excessive pressure on state broad-based taxes, and the failure of state aid to bring financial support to municipalities. The final trend has been the impact of tax sacrifice.