Property tax inequity resulting from inaccurate assessment—The Taiwan experience

Real properties are periodically valued by governments in order to perform a variety of public functions. Time and resource constraints have often motivated a government to develop adhoc assessment rules to undertake expeditious valuation. The extent to which the properties are equitably valued, however, should be under constant scrutiny. Valuation equity is defined as properties being valued at the same, or similar, percentage of their sales price in the market. Violation of the equity criterion is deemed as evidence of valuation inequity. This study employs and expands the concept of assessment ratios to detect, and explain where possible, the property valuation inequity in Taipei City. Empirical evidence suggests no significant assessment regressivity or progressivity among individual properties. The assessment ratios between houses, low-rise condominiums, and high-rise condominiums, nevertheless, are found to be materially different. Spatial consideration is also explicitly added into the analysis. A distinct clustering of neighborhoods with similar assessment ratios is found. This non-random pattern infers valuation inequity in a spatial sense. The spatial inequity of assessment ratios suggests that certain location-associated social and economic price-determining factors are not properly accounted for in the assessment rules. The extraction method adopted by assessment rules to apportion land and structure values is believed to be responsible. A likely cause for the malfunction of the extraction method is thought to be the widely documented non-linear site size–land value relationship. After all, high buildings on sites that feature multi-ownership dominate the majority of areas in Taipei.