Which factor does not contribute to external obsolescence?

External obsolescence refers to the loss of value of a property due to external factors that are typically beyond the control of the property owner. This can include economic conditions, changes in the neighborhood, and environmental issues.

The structural age of the property pertains to its physical condition and the depreciation over time or the aging of the building itself. While the age of a structure can influence its market value, it is an internal factor related to the property itself rather than an external factor affecting its environment and marketability.

In contrast, factors such as changes in neighborhood demographics, air pollution, and increased traffic are all external conditions that can negatively impact property values. These changes outside of the property can lead to a decline in desirability, thus contributing to external obsolescence.