11/07/2025
This is part 4 in a series where I'm hoping to reframe the appraisal problem in a way that will change our perspective on how we approach the field of valuation, and the associated techniques and processes to arrive at an opinion of value.
In the last post, I agreed wholeheartedly with a comment that, "Appraisal is not rocket science." That's true, but not in the way that the phrase is typically used.
Rocket science is deterministic
Appraisal isn't.
The process of valuation takes place within 'interdeterminate' systems. 'Interdeterminacy' is literally 'the state of being mutually determined'. I coined this term (at least for use in this context) to refer to systems in which at least some of the constituent variables are interactive, or mutually constraining, such that each variable may help to determine the others.
In the last post, I demonstrated mathematical indeterminacy, where the system lacks sufficient data to be solved. While limited information is also a feature of real world systems (aka, markets), these systems are best described as interdeterminate, where interactions between variables themselves create at least a partially undetermined system.
At first, it might sound like correlation, but correlation only measures co-movement. Interdeterminacy goes deeper. It describes mutual influence.
Here are a couple of simple examples:
1) The cost of remodeling a larger home is higher than the cost of remodeling a smaller home, so differences in condition aren't just correlated with size, they are partly caused by it.
2) The traffic influence from an adjacent busy street can depend on the interplay of variables such as lot size, lot shape, and frontage (among others). It's not mere correlation. The extent to which that adverse influence is experienced is dependent upon other variables.
In interdeterminate systems each variable's effect exists in relation to other variables. These systems defy determinism and rely on probabilistic reasoning, methods, and descriptions.
In the next post, I'll break down interdeterminacies into two types.