The evaluation of accuracy and uniformity in the mass valuation of properties in the city of Johannesburg, South Africa

Purpose The study arose because of myriad objections and consequent appeals to the tribunals regarding the municipal valuation estimates. This paper assesses valuation accuracy and uniformity levels relating to the City of Johannesburg's (CoJ's) general valuation roll (GVR) of 2018. Design/methodology/approach The study adopts a quantitative approach underpinned by descriptive and inferential statistics. These statistical tools, including the Assessment Sales Ratio (ASR), Mean Absolute Percentage Error (MAPE), and Root Mean Squared Error (RMSE), were applied to a sample of secondary data on property assessments and sales obtained from the CoJ. The Price Related Differential (PRD), Price Related Bias (PRB), and Coefficient of Dispersion (COD) were used to test uniformity. Findings The results reveal the Median ASR, MAPE, and RMSE at 0.90, 19.05%, and R123,514.66, respectively. The uniformity measures for PRD, PRB, and COD are 1.02, −0.01, and 18.87%, respectively. In keeping with the IAAO standards, these results suggest an acceptable degree of accuracy and uniformity, which is fair to the rate payers of the low-valued properties. The results also underscore the critical need for the post-valuation date ratio analysis in South African municipalities, a step that cannot be delayed. Research limitations/implications The study relates to the compelling need for post-valuation independent ratio studies conducted on the GVRs, with specific consideration given to the assessed values. After the valuation date, the property sales were not sufficiently large for the sample; hence, remedial measures were taken to improve the sample's representativeness. Originality/value This is the first time a post-valuation date study on accuracy and uniformity of value estimates has been done in South Africa, thus proving an independent audit on the GVRs. Extending such practice to all local property rates and taxes municipalities in South Africa is imperative, as it would enhance public confidence in municipal valuation.