Mass appraisal of real property is a tool for evaluation of a large number of real property. It is determined by standardized procedures and valuation models on a given day. The Surveying and Mapping Authority of the Republic of Slovenia manages data on real estate sales and rents transactions in Slovenia. There are relatively few sales for commercial real property on the Slovenian real estate market. This paper deals with an attempt to define and model the calibration of rent as a support for mass appraisal model for offices through statistical analysis with the GAMLSS (Generalized Additive Models for Location, Scale and Shape) model. Results of the study show that rents for offices are most affected by location, size of rented area, age of the building, the duration of the lease, and the inclusion of operating costs in the rent. Because model-based GAMLSS cannot be expressed with simple equations, the model is finally simplified to a level comparable to mass appraisal of real property.

Key words: mass appraisal, real estate, rent, office