In Oregon Tax Rates Measure 50 replaced most tax levies with permanent tax rates. Therefore, the exercise of setting tax rates remains only for local option levies, bond levies, and urban renewal special levies. Under Measure 50, the county assessor computes tax rates for local option levies, bond levies, and urban renewal special levies, and then adds those rates to the permanent rates to compute the total rate to be extended to a property. The tax extended to a property is the total tax rate multiplied by the assessed value of the property.
Under the pre-Measure 50 systems, the county assessor extended authorized levies and computed district tax rates for each taxing district. District tax rates were expressed as a dollar amount per $1,000 of assessed value, and were computed by dividing total taxes levied by the total assessed value inside the taxing district boundaries. The total tax extended to a property was the sum of the district tax rates multiplied by the assessed value of the property. Under Measure 5, if the tax extended to the property exceeded the Measure 5 limits, the tax going to each local government was reduced proportionally until the limit was reached. When Measure 50 first took effect in the 1997-98 tax year, permanent tax rates were calculated based on a complicated formula that took into account several factors. These included: a) the amount of taxes that would have been raised in 1997-98 under Measure 47, b) the levies that existed under the Measure 5 system, c) the tax cut required by Measure 50, and d) a variety of special provisions that exempted certain types of levies from the Measure 50 cuts, and reduced the amount of the tax cuts for districts with rapid assessed value growth due to new construction.
Use the link above for a .pdf of the full Oregon Property Tax explanation