Which of the following is not a characteristic that cannot influence an appraiser's opinion of value?

The characteristic that does not influence an appraiser's opinion of value is property size. Property size is a factual element that directly influences value because it affects the usable area, marketability, and potential for development or usage of the property.

In appraisal practice, characteristics such as race, age, and income level are considered unethical criteria that can lead to bias and discrimination. The Uniform Standards of Professional Appraisal Practice (USPAP) stipulate that appraisers must remain objective and base their opinions of value solely on relevant property characteristics and market data. Therefore, personal attributes or socio-economic factors should not play a role in determining value, which is why property size is the only characteristic in the list that relates directly to the physical attributes of the property itself. The focus on factual data like property size helps maintain the integrity and objectivity of the appraisal process.